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Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the word or phrase that best fits each of the numbered blanks.Ever since it was first possible to make a real robot, people have been hoping for the invention of a machine that would do all the necessary jobs around the house. If boring and repetitive factory work could be (37) ________ by robots, why not boring and repetitive household chores too? For a long time the only people who really gave the problem their attention were amateur inventors And they came up against a major difficulty. That is, housework is actually very complex It has never been one job it has always been many. A factor robot (38) ________ one task endlessly until it is reprogrammed to do something else. It doesn’t run the whole factory. A housework robot on the other hand, has to do several different (39) ________ of cleaning and carrying jobs and also has to cope (40) ________ all the different shapes and positions of rooms, furniture, ornaments, cats and dogs. (41) ________, there have been some developments recently. Sensors are available to help the robot locate objects and avoid obstacles. We have the technology to produce the hardware. All that is missing the software- the programs that will operate the machine.Question 41:
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the word or phrase that best fits each of the numbered blanks.Ever since it was first possible to make a real robot, people have been hoping for the invention of a machine that would do all the necessary jobs around the house. If boring and repetitive factory work could be (37) ________ by robots, why not boring and repetitive household chores too? For a long time the only people who really gave the problem their attention were amateur inventors And they came up against a major difficulty. That is, housework is actually very complex It has never been one job it has always been many. A factor robot (38) ________ one task endlessly until it is reprogrammed to do something else. It doesn’t run the whole factory. A housework robot on the other hand, has to do several different (39) ________ of cleaning and carrying jobs and also has to cope (40) ________ all the different shapes and positions of rooms, furniture, ornaments, cats and dogs. (41) ________, there have been some developments recently. Sensors are available to help the robot locate objects and avoid obstacles. We have the technology to produce the hardware. All that is missing the software- the programs that will operate the machine.Question 40
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the word or phrase that best fits each of the numbered blanks.Ever since it was first possible to make a real robot, people have been hoping for the invention of a machine that would do all the necessary jobs around the house. If boring and repetitive factory work could be (37) ________ by robots, why not boring and repetitive household chores too? For a long time the only people who really gave the problem their attention were amateur inventors And they came up against a major difficulty. That is, housework is actually very complex It has never been one job it has always been many. A factor robot (38) ________ one task endlessly until it is reprogrammed to do something else. It doesn’t run the whole factory. A housework robot on the other hand, has to do several different (39) ________ of cleaning and carrying jobs and also has to cope (40) ________ all the different shapes and positions of rooms, furniture, ornaments, cats and dogs. (41) ________, there have been some developments recently. Sensors are available to help the robot locate objects and avoid obstacles. We have the technology to produce the hardware. All that is missing the software- the programs that will operate the machine.Question 39:
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the word or phrase that best fits each of the numbered blanks.Ever since it was first possible to make a real robot, people have been hoping for the invention of a machine that would do all the necessary jobs around the house. If boring and repetitive factory work could be (37) ________ by robots, why not boring and repetitive household chores too? For a long time the only people who really gave the problem their attention were amateur inventors And they came up against a major difficulty. That is, housework is actually very complex It has never been one job it has always been many. A factor robot (38) ________ one task endlessly until it is reprogrammed to do something else. It doesn’t run the whole factory. A housework robot on the other hand, has to do several different (39) ________ of cleaning and carrying jobs and also has to cope (40) ________ all the different shapes and positions of rooms, furniture, ornaments, cats and dogs. (41) ________, there have been some developments recently. Sensors are available to help the robot locate objects and avoid obstacles. We have the technology to produce the hardware. All that is missing the software- the programs that will operate the machine.Question 38:
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the word or phrase that best fits each of the numbered blanks.Ever since it was first possible to make a real robot, people have been hoping for the invention of a machine that would do all the necessary jobs around the house. If boring and repetitive factory work could be (37) ________ by robots, why not boring and repetitive household chores too? For a long time the only people who really gave the problem their attention were amateur inventors And they came up against a major difficulty. That is, housework is actually very complex It has never been one job it has always been many. A factor robot (38) ________ one task endlessly until it is reprogrammed to do something else. It doesn’t run the whole factory. A housework robot on the other hand, has to do several different (39) ________ of cleaning and carrying jobs and also has to cope (40) ________ all the different shapes and positions of rooms, furniture, ornaments, cats and dogs. (41) ________, there have been some developments recently. Sensors are available to help the robot locate objects and avoid obstacles. We have the technology to produce the hardware. All that is missing the software- the programs that will operate the machine.Question 37:
Read the following passage and write the letter A, B, C or D on the top of the first page to indicate the correct answer to each of the questions.In the course of its history, human inventions have dramatically increased the average amount of energy available for use per person. Primitive peoples in cold regions burned wood and animal dung to heat their caves, cook food, and drive off animals by fire. The first step toward the developing of more efficient fuels was taken when people discovered that they could use vegetable oils and animal fats in lieu of gathered or cut wood. Charcoal gave off more intensive heat than wood and was more easily obtainable than organic fats. The Greeks first began to use coal for metal smelting in the 4th century, but it did not come into extensive use until the Industrial Revolution. In the 1700s, at the beginning of the Industrial Revolution, most energy used in the United States and other nations undergoing industrialization was obtained from perpetual and renewable sources, such as wood, water streams, domesticated animal labor, and wind. These were predominantly locally available supplies. By mid-1800s, 91 percent of all commercial energy consumed in the United States and European countries was obtained from wood. However, at he beginning of the 20th century, coal became a major energy source and replaced wood in industrializing countries. Although in most regions and climate zones wood was more readily accessible than coal, the latter represents a more concentrated source of energy. In 1910, natural gas and oil firmly replaced coal as the main source of fuel because they are lighter and, therefore, cheaper to transport. They burned more cleanly than coal and polluted less. Unlike coal, oil could be refined to manufacture liquid fuels for vehicles, a very important consideration in the early 1900s, when the automobile arrived on the scene.By 1984, non-renewable fossil fuels, such as oil, coal, and natural gas, provided over 82 percent of the commercial and industrial energy used in the world. Small amounts of energy were derived from nuclear fission, and the remaining 16 percent came from burning direct perpetual and renewable fuels, such as biomass. Between 1700 and 1986, a large number of countries shifted from the use of energy from local sources to a centralized generation of hydropower and solar energy converted to electricity. The energy derived from non-renewable fossil fuels has been increasingly produced in one location and transported to another, as is the case with most automobile fuels. In countries with private, rather than public transportation, the age of non-renewable fuels has created a dependency on a finite resource that will have to be replaced.Alternative fuel sources are numerous, and shale oil and hydrocarbons are just two examples. The extraction of shale oil from large deposits in Asian and European regions has proven to be labor consuming and costly. The resulting product is sulfur-and nitrogen-rich, and large scale extractions are presently prohibitive. Similarly, the extraction of hydrocarbons from tar sands in Alberta and Utah is complex. Semi-solid hydrocarbons cannot be easily separated from the sandstone and limestone that carry them, and modern technology is not sufficiently versatile for a large-scale removal of the material. However, both sources of fuel may eventually be needed as petroleum prices continue to rise and limitations in fossil fuel availability make alternative deposits more attractive.Question:The word “prohibitive” is closest in meaning to
Read the following passage and write the letter A, B, C or D on the top of the first page to indicate the correct answer to each of the questions.In the course of its history, human inventions have dramatically increased the average amount of energy available for use per person. Primitive peoples in cold regions burned wood and animal dung to heat their caves, cook food, and drive off animals by fire. The first step toward the developing of more efficient fuels was taken when people discovered that they could use vegetable oils and animal fats in lieu of gathered or cut wood. Charcoal gave off more intensive heat than wood and was more easily obtainable than organic fats. The Greeks first began to use coal for metal smelting in the 4th century, but it did not come into extensive use until the Industrial Revolution. In the 1700s, at the beginning of the Industrial Revolution, most energy used in the United States and other nations undergoing industrialization was obtained from perpetual and renewable sources, such as wood, water streams, domesticated animal labor, and wind. These were predominantly locally available supplies. By mid-1800s, 91 percent of all commercial energy consumed in the United States and European countries was obtained from wood. However, at he beginning of the 20th century, coal became a major energy source and replaced wood in industrializing countries. Although in most regions and climate zones wood was more readily accessible than coal, the latter represents a more concentrated source of energy. In 1910, natural gas and oil firmly replaced coal as the main source of fuel because they are lighter and, therefore, cheaper to transport. They burned more cleanly than coal and polluted less. Unlike coal, oil could be refined to manufacture liquid fuels for vehicles, a very important consideration in the early 1900s, when the automobile arrived on the scene.By 1984, non-renewable fossil fuels, such as oil, coal, and natural gas, provided over 82 percent of the commercial and industrial energy used in the world. Small amounts of energy were derived from nuclear fission, and the remaining 16 percent came from burning direct perpetual and renewable fuels, such as biomass. Between 1700 and 1986, a large number of countries shifted from the use of energy from local sources to a centralized generation of hydropower and solar energy converted to electricity. The energy derived from non-renewable fossil fuels has been increasingly produced in one location and transported to another, as is the case with most automobile fuels. In countries with private, rather than public transportation, the age of non-renewable fuels has created a dependency on a finite resource that will have to be replaced.Alternative fuel sources are numerous, and shale oil and hydrocarbons are just two examples. The extraction of shale oil from large deposits in Asian and European regions has proven to be labor consuming and costly. The resulting product is sulfur-and nitrogen-rich, and large scale extractions are presently prohibitive. Similarly, the extraction of hydrocarbons from tar sands in Alberta and Utah is complex. Semi-solid hydrocarbons cannot be easily separated from the sandstone and limestone that carry them, and modern technology is not sufficiently versatile for a large-scale removal of the material. However, both sources of fuel may eventually be needed as petroleum prices continue to rise and limitations in fossil fuel availability make alternative deposits more attractive.Question:The author of the passage implies that alternative sources of fuel are curently
Read the following passage and write the letter A, B, C or D on the top of the first page to indicate the correct answer to each of the questions.In the course of its history, human inventions have dramatically increased the average amount of energy available for use per person. Primitive peoples in cold regions burned wood and animal dung to heat their caves, cook food, and drive off animals by fire. The first step toward the developing of more efficient fuels was taken when people discovered that they could use vegetable oils and animal fats in lieu of gathered or cut wood. Charcoal gave off more intensive heat than wood and was more easily obtainable than organic fats. The Greeks first began to use coal for metal smelting in the 4th century, but it did not come into extensive use until the Industrial Revolution. In the 1700s, at the beginning of the Industrial Revolution, most energy used in the United States and other nations undergoing industrialization was obtained from perpetual and renewable sources, such as wood, water streams, domesticated animal labor, and wind. These were predominantly locally available supplies. By mid-1800s, 91 percent of all commercial energy consumed in the United States and European countries was obtained from wood. However, at he beginning of the 20th century, coal became a major energy source and replaced wood in industrializing countries. Although in most regions and climate zones wood was more readily accessible than coal, the latter represents a more concentrated source of energy. In 1910, natural gas and oil firmly replaced coal as the main source of fuel because they are lighter and, therefore, cheaper to transport. They burned more cleanly than coal and polluted less. Unlike coal, oil could be refined to manufacture liquid fuels for vehicles, a very important consideration in the early 1900s, when the automobile arrived on the scene.By 1984, non-renewable fossil fuels, such as oil, coal, and natural gas, provided over 82 percent of the commercial and industrial energy used in the world. Small amounts of energy were derived from nuclear fission, and the remaining 16 percent came from burning direct perpetual and renewable fuels, such as biomass. Between 1700 and 1986, a large number of countries shifted from the use of energy from local sources to a centralized generation of hydropower and solar energy converted to electricity. The energy derived from non-renewable fossil fuels has been increasingly produced in one location and transported to another, as is the case with most automobile fuels. In countries with private, rather than public transportation, the age of non-renewable fuels has created a dependency on a finite resource that will have to be replaced.Alternative fuel sources are numerous, and shale oil and hydrocarbons are just two examples. The extraction of shale oil from large deposits in Asian and European regions has proven to be labor consuming and costly. The resulting product is sulfur-and nitrogen-rich, and large scale extractions are presently prohibitive. Similarly, the extraction of hydrocarbons from tar sands in Alberta and Utah is complex. Semi-solid hydrocarbons cannot be easily separated from the sandstone and limestone that carry them, and modern technology is not sufficiently versatile for a large-scale removal of the material. However, both sources of fuel may eventually be needed as petroleum prices continue to rise and limitations in fossil fuel availability make alternative deposits more attractive.Question:It can be inferred from the passage that in the early 20th centurgy, energy was obtained primarily from
Read the following passage and write the letter A, B, C or D on the top of the first page to indicate the correct answer to each of the questions.In the course of its history, human inventions have dramatically increased the average amount of energy available for use per person. Primitive peoples in cold regions burned wood and animal dung to heat their caves, cook food, and drive off animals by fire. The first step toward the developing of more efficient fuels was taken when people discovered that they could use vegetable oils and animal fats in lieu of gathered or cut wood. Charcoal gave off more intensive heat than wood and was more easily obtainable than organic fats. The Greeks first began to use coal for metal smelting in the 4th century, but it did not come into extensive use until the Industrial Revolution. In the 1700s, at the beginning of the Industrial Revolution, most energy used in the United States and other nations undergoing industrialization was obtained from perpetual and renewable sources, such as wood, water streams, domesticated animal labor, and wind. These were predominantly locally available supplies. By mid-1800s, 91 percent of all commercial energy consumed in the United States and European countries was obtained from wood. However, at he beginning of the 20th century, coal became a major energy source and replaced wood in industrializing countries. Although in most regions and climate zones wood was more readily accessible than coal, the latter represents a more concentrated source of energy. In 1910, natural gas and oil firmly replaced coal as the main source of fuel because they are lighter and, therefore, cheaper to transport. They burned more cleanly than coal and polluted less. Unlike coal, oil could be refined to manufacture liquid fuels for vehicles, a very important consideration in the early 1900s, when the automobile arrived on the scene.By 1984, non-renewable fossil fuels, such as oil, coal, and natural gas, provided over 82 percent of the commercial and industrial energy used in the world. Small amounts of energy were derived from nuclear fission, and the remaining 16 percent came from burning direct perpetual and renewable fuels, such as biomass. Between 1700 and 1986, a large number of countries shifted from the use of energy from local sources to a centralized generation of hydropower and solar energy converted to electricity. The energy derived from non-renewable fossil fuels has been increasingly produced in one location and transported to another, as is the case with most automobile fuels. In countries with private, rather than public transportation, the age of non-renewable fuels has created a dependency on a finite resource that will have to be replaced.Alternative fuel sources are numerous, and shale oil and hydrocarbons are just two examples. The extraction of shale oil from large deposits in Asian and European regions has proven to be labor consuming and costly. The resulting product is sulfur-and nitrogen-rich, and large scale extractions are presently prohibitive. Similarly, the extraction of hydrocarbons from tar sands in Alberta and Utah is complex. Semi-solid hydrocarbons cannot be easily separated from the sandstone and limestone that carry them, and modern technology is not sufficiently versatile for a large-scale removal of the material. However, both sources of fuel may eventually be needed as petroleum prices continue to rise and limitations in fossil fuel availability make alternative deposits more attractive.Question:According to the passage, what was the greatest advantage of oil as fuel?
Read the following passage and write the letter A, B, C or D on the top of the first page to indicate the correct answer to each of the questions.In the course of its history, human inventions have dramatically increased the average amount of energy available for use per person. Primitive peoples in cold regions burned wood and animal dung to heat their caves, cook food, and drive off animals by fire. The first step toward the developing of more efficient fuels was taken when people discovered that they could use vegetable oils and animal fats in lieu of gathered or cut wood. Charcoal gave off more intensive heat than wood and was more easily obtainable than organic fats. The Greeks first began to use coal for metal smelting in the 4th century, but it did not come into extensive use until the Industrial Revolution. In the 1700s, at the beginning of the Industrial Revolution, most energy used in the United States and other nations undergoing industrialization was obtained from perpetual and renewable sources, such as wood, water streams, domesticated animal labor, and wind. These were predominantly locally available supplies. By mid-1800s, 91 percent of all commercial energy consumed in the United States and European countries was obtained from wood. However, at he beginning of the 20th century, coal became a major energy source and replaced wood in industrializing countries. Although in most regions and climate zones wood was more readily accessible than coal, the latter represents a more concentrated source of energy. In 1910, natural gas and oil firmly replaced coal as the main source of fuel because they are lighter and, therefore, cheaper to transport. They burned more cleanly than coal and polluted less. Unlike coal, oil could be refined to manufacture liquid fuels for vehicles, a very important consideration in the early 1900s, when the automobile arrived on the scene.By 1984, non-renewable fossil fuels, such as oil, coal, and natural gas, provided over 82 percent of the commercial and industrial energy used in the world. Small amounts of energy were derived from nuclear fission, and the remaining 16 percent came from burning direct perpetual and renewable fuels, such as biomass. Between 1700 and 1986, a large number of countries shifted from the use of energy from local sources to a centralized generation of hydropower and solar energy converted to electricity. The energy derived from non-renewable fossil fuels has been increasingly produced in one location and transported to another, as is the case with most automobile fuels. In countries with private, rather than public transportation, the age of non-renewable fuels has created a dependency on a finite resource that will have to be replaced.Alternative fuel sources are numerous, and shale oil and hydrocarbons are just two examples. The extraction of shale oil from large deposits in Asian and European regions has proven to be labor consuming and costly. The resulting product is sulfur-and nitrogen-rich, and large scale extractions are presently prohibitive. Similarly, the extraction of hydrocarbons from tar sands in Alberta and Utah is complex. Semi-solid hydrocarbons cannot be easily separated from the sandstone and limestone that carry them, and modern technology is not sufficiently versatile for a large-scale removal of the material. However, both sources of fuel may eventually be needed as petroleum prices continue to rise and limitations in fossil fuel availability make alternative deposits more attractive.Question:The phrase “the latter” refers to
Read the following passage and write the letter A, B, C or D on the top of the first page to indicate the correct answer to each of the questions.In the course of its history, human inventions have dramatically increased the average amount of energy available for use per person. Primitive peoples in cold regions burned wood and animal dung to heat their caves, cook food, and drive off animals by fire. The first step toward the developing of more efficient fuels was taken when people discovered that they could use vegetable oils and animal fats in lieu of gathered or cut wood. Charcoal gave off more intensive heat than wood and was more easily obtainable than organic fats. The Greeks first began to use coal for metal smelting in the 4th century, but it did not come into extensive use until the Industrial Revolution. In the 1700s, at the beginning of the Industrial Revolution, most energy used in the United States and other nations undergoing industrialization was obtained from perpetual and renewable sources, such as wood, water streams, domesticated animal labor, and wind. These were predominantly locally available supplies. By mid-1800s, 91 percent of all commercial energy consumed in the United States and European countries was obtained from wood. However, at he beginning of the 20th century, coal became a major energy source and replaced wood in industrializing countries. Although in most regions and climate zones wood was more readily accessible than coal, the latter represents a more concentrated source of energy. In 1910, natural gas and oil firmly replaced coal as the main source of fuel because they are lighter and, therefore, cheaper to transport. They burned more cleanly than coal and polluted less. Unlike coal, oil could be refined to manufacture liquid fuels for vehicles, a very important consideration in the early 1900s, when the automobile arrived on the scene.By 1984, non-renewable fossil fuels, such as oil, coal, and natural gas, provided over 82 percent of the commercial and industrial energy used in the world. Small amounts of energy were derived from nuclear fission, and the remaining 16 percent came from burning direct perpetual and renewable fuels, such as biomass. Between 1700 and 1986, a large number of countries shifted from the use of energy from local sources to a centralized generation of hydropower and solar energy converted to electricity. The energy derived from non-renewable fossil fuels has been increasingly produced in one location and transported to another, as is the case with most automobile fuels. In countries with private, rather than public transportation, the age of non-renewable fuels has created a dependency on a finite resource that will have to be replaced.Alternative fuel sources are numerous, and shale oil and hydrocarbons are just two examples. The extraction of shale oil from large deposits in Asian and European regions has proven to be labor consuming and costly. The resulting product is sulfur-and nitrogen-rich, and large scale extractions are presently prohibitive. Similarly, the extraction of hydrocarbons from tar sands in Alberta and Utah is complex. Semi-solid hydrocarbons cannot be easily separated from the sandstone and limestone that carry them, and modern technology is not sufficiently versatile for a large-scale removal of the material. However, both sources of fuel may eventually be needed as petroleum prices continue to rise and limitations in fossil fuel availability make alternative deposits more attractive.Question:The author of the passage implies that in the 1700s, sources of energy were
Read the following passage and write the letter A, B, C or D on the top of the first page to indicate the correct answer to each of the questions.In the course of its history, human inventions have dramatically increased the average amount of energy available for use per person. Primitive peoples in cold regions burned wood and animal dung to heat their caves, cook food, and drive off animals by fire. The first step toward the developing of more efficient fuels was taken when people discovered that they could use vegetable oils and animal fats in lieu of gathered or cut wood. Charcoal gave off more intensive heat than wood and was more easily obtainable than organic fats. The Greeks first began to use coal for metal smelting in the 4th century, but it did not come into extensive use until the Industrial Revolution. In the 1700s, at the beginning of the Industrial Revolution, most energy used in the United States and other nations undergoing industrialization was obtained from perpetual and renewable sources, such as wood, water streams, domesticated animal labor, and wind. These were predominantly locally available supplies. By mid-1800s, 91 percent of all commercial energy consumed in the United States and European countries was obtained from wood. However, at he beginning of the 20th century, coal became a major energy source and replaced wood in industrializing countries. Although in most regions and climate zones wood was more readily accessible than coal, the latter represents a more concentrated source of energy. In 1910, natural gas and oil firmly replaced coal as the main source of fuel because they are lighter and, therefore, cheaper to transport. They burned more cleanly than coal and polluted less. Unlike coal, oil could be refined to manufacture liquid fuels for vehicles, a very important consideration in the early 1900s, when the automobile arrived on the scene.By 1984, non-renewable fossil fuels, such as oil, coal, and natural gas, provided over 82 percent of the commercial and industrial energy used in the world. Small amounts of energy were derived from nuclear fission, and the remaining 16 percent came from burning direct perpetual and renewable fuels, such as biomass. Between 1700 and 1986, a large number of countries shifted from the use of energy from local sources to a centralized generation of hydropower and solar energy converted to electricity. The energy derived from non-renewable fossil fuels has been increasingly produced in one location and transported to another, as is the case with most automobile fuels. In countries with private, rather than public transportation, the age of non-renewable fuels has created a dependency on a finite resource that will have to be replaced.Alternative fuel sources are numerous, and shale oil and hydrocarbons are just two examples. The extraction of shale oil from large deposits in Asian and European regions has proven to be labor consuming and costly. The resulting product is sulfur-and nitrogen-rich, and large scale extractions are presently prohibitive. Similarly, the extraction of hydrocarbons from tar sands in Alberta and Utah is complex. Semi-solid hydrocarbons cannot be easily separated from the sandstone and limestone that carry them, and modern technology is not sufficiently versatile for a large-scale removal of the material. However, both sources of fuel may eventually be needed as petroleum prices continue to rise and limitations in fossil fuel availability make alternative deposits more attractive.Question:It can be inferred from the first paragraph that
Read the following passage and write the letter A, B, C or D on the top of the first page to indicate the correct answer to each of the questions.In the course of its history, human inventions have dramatically increased the average amount of energy available for use per person. Primitive peoples in cold regions burned wood and animal dung to heat their caves, cook food, and drive off animals by fire. The first step toward the developing of more efficient fuels was taken when people discovered that they could use vegetable oils and animal fats in lieu of gathered or cut wood. Charcoal gave off more intensive heat than wood and was more easily obtainable than organic fats. The Greeks first began to use coal for metal smelting in the 4th century, but it did not come into extensive use until the Industrial Revolution. In the 1700s, at the beginning of the Industrial Revolution, most energy used in the United States and other nations undergoing industrialization was obtained from perpetual and renewable sources, such as wood, water streams, domesticated animal labor, and wind. These were predominantly locally available supplies. By mid-1800s, 91 percent of all commercial energy consumed in the United States and European countries was obtained from wood. However, at he beginning of the 20th century, coal became a major energy source and replaced wood in industrializing countries. Although in most regions and climate zones wood was more readily accessible than coal, the latter represents a more concentrated source of energy. In 1910, natural gas and oil firmly replaced coal as the main source of fuel because they are lighter and, therefore, cheaper to transport. They burned more cleanly than coal and polluted less. Unlike coal, oil could be refined to manufacture liquid fuels for vehicles, a very important consideration in the early 1900s, when the automobile arrived on the scene.By 1984, non-renewable fossil fuels, such as oil, coal, and natural gas, provided over 82 percent of the commercial and industrial energy used in the world. Small amounts of energy were derived from nuclear fission, and the remaining 16 percent came from burning direct perpetual and renewable fuels, such as biomass. Between 1700 and 1986, a large number of countries shifted from the use of energy from local sources to a centralized generation of hydropower and solar energy converted to electricity. The energy derived from non-renewable fossil fuels has been increasingly produced in one location and transported to another, as is the case with most automobile fuels. In countries with private, rather than public transportation, the age of non-renewable fuels has created a dependency on a finite resource that will have to be replaced.Alternative fuel sources are numerous, and shale oil and hydrocarbons are just two examples. The extraction of shale oil from large deposits in Asian and European regions has proven to be labor consuming and costly. The resulting product is sulfur-and nitrogen-rich, and large scale extractions are presently prohibitive. Similarly, the extraction of hydrocarbons from tar sands in Alberta and Utah is complex. Semi-solid hydrocarbons cannot be easily separated from the sandstone and limestone that carry them, and modern technology is not sufficiently versatile for a large-scale removal of the material. However, both sources of fuel may eventually be needed as petroleum prices continue to rise and limitations in fossil fuel availability make alternative deposits more attractive.Question:What is the main topic of the passage?