15000 bài tập tách từ đề thi thử môn Tiếng Anh có đáp án (Phần 75)

These days, most people in Britain and the US do not wear very formal clothes. But sometimes it is important to wear the right thing.

Many British people don't think about clothes very much. They just like to be comfortable. When they go out to enjoy themselves, they can wear almost anything. At theatres, cinemas and concerts you can put on what you like from elegant suits and dresses to jeans and sweaters. Anything goes, as long as you look clean and tidy.

But in Britain, as well as in the US, men in offices usually wear suits and ties, and women wear dresses or skirts (not trousers). Doctors, lawyers and business people wear quite formal clothes. And in some hotels and restaurants men have to wear ties and women wear smart dresses.

In many years, Americans are more relaxed than British people, but they are more careful with their clothes. At home, or on holiday, most Americans wear informal or sporty clothes. But when they go out in the evening, they like to look elegant. In good hotels and restaurants, men have to wear jackets and ties, and women wear pretty clothes and smart hairstyles.

It is difficult to say exactly what people wear informal or formal in Britain and the US, because everyone is different. If you are not sure what to wear, watch what other people do and then do the same. You'll feel more relaxed if you don't look too different from everyone else.

Under certain circumstances, the human body must cope with gases at greater-than-normal atmospheric pressure. For example, gas pressures increase rapidly during a drive made with scuba gear because the breathing equipment allows divers to stay underwater longer and dive deeper. The pressure exerted on the human body increases by 1 atmosphere for every 10 meters of depth in seawater, so that at 39 meters in seawater a diver is exposed to pressure of about 4 atmospheres. The pressure of the gases being breathed must equal the external pressure applied to the body, otherwise breathing is very difficult. Therefore all of the gases in the air breathed by a scuba diver at 40 meter are present at five times their usual pressure. Nitrogen, which composes 80 percent of the air we breathe, usually causes a balmy feeling of well-being at this pressure. At a depth of 5 atmospheres, nitrogen causes symptoms resembling alcohol intoxication, known as nitrogen narcosis. Nitrogen narcosis apparently results from a direct effect on the brain of the large amounts of nitrogen dissolved in the blood. Deep dives are less dangerous if helium is substituted for nitrogen, because under these pressures helium does not exert a similar narcotic effect.

As a scuba diver descends, the pressure of nitrogen on the lungs increases. Nitrogen then diffuses from the lungs to the blood, and from the blood to body tissues. Nitrogen then diffuses from the lungs to the blood, and from the blood to body tissues The reverse occurs when the diver surfaces, the nitrogen pressure in the lungs falls and the nitrogen diffuses from the tissues into the blood, and from the blood into the lungs. If the return to the surface is too rapid, nitrogen in the tissues and blood cannot diffuse out rapidly enough and nitrogen bubbles are formed. They can cause severe pains, particularly around the joints.

Another complication may result if the breath is held during ascent. During ascent from a depth of 10 meters, the volume of air in the lungs will double because the air pressure at the surface is only half of what it was at 10 meters. This change in volume may cause the lungs to distend and even rupture. This condition is called air embolism.

To avoid this event, a diver must ascend slowly, never at a rate exceeding the rise of the exhaled air bubbles, and must exhale during ascent.

Music can bring us to tears or to our feet, drive us into battle or lull us to sleep. Music is indeed remarkable in its power over all humankind, and perhaps for that very reason, no human culture on earth has ever lived without it. From discoveries made in France and Slovenia, even Neanderthal man, as long as 53,000 years ago, had developed surprisingly sophisticated, sweet-sounding flutes carved from animal bones. It is perhaps then, no accident that music should strike such a chord with the limbic system – an ancient part of our brain, evolutionarily speaking, and one that we share with much of the animal kingdom. Some researchers even propose that music came into this world long before the human race ever did. For example, the fact that whale and human music have so much in common even though our evolutionary paths have not intersected for nearly 60 million years suggests that music may predate humans. They assert that rather than being the inventors of music, we are latecomers to the musical scene.

Humpback whale composers employ many of the same tricks that human songwriters do. In addition to using similar rhythms, humpbacks keep musical phrases to a few seconds, creating themes out of several phrases before singing the next one. Whale songs in general are no longer than symphony movements, perhaps because they have a similar attention span. Even though they can sing over a range of seven octaves, the whales typically sing in key, spreading adjacent notes no farther apart than a scale. They mix percussive and pure tones in pretty much the same ratios as human composers – and follow their ABA form, in which a theme is presented, elaborated on and then revisited in a slightly modified form. Perhaps most amazing, humpback whale songs include repeating refrains that rhyme. It has been suggested that whales might use rhymes for exactly the same reasons that we do: as devices to help them remember. Whale songs can also be rather catchy. When a few humpbacks from the Indian Ocean strayed into the Pacific, some of the whales they met there quickly changed their tunes – singing the new whales’ songs within three short years. Some scientists are even tempted to speculate that a universal music awaits discovery.

Millions of people are using cell phones today. In many places, it is actually considered unusual not to use one. In many countries, cell phones are very popular with young people. They find that the phones are more than a means of communication - having a mobile phone shows that they are cool and connected.

The explosion in mobile phone use around the world has made some health professionals worried. Some doctors are concerned that in the future many people may suffer health problems from the use of mobile phones. In England, there has been a serious debate about this issue. Mobile phone companies are worried about the negative publicity of such ideas. They say that there is no proof that mobile phones are bad for your health.

On the other hand, medical studies have shown changes in the brain cells of some people who use mobile phones. Signs of change in the tissues of the brain and head can be detected with modern scanning equipment. In one case, a travelling salesman had to retire at young age because of serious memory loss. He couldn't remember even simple tasks. He would often forget the name of his own son. This man used to talk on his mobile phone for about six hours a day, every day of his working week, for a couple of years. His family doctor blamed his mobile phone use, but his employer's doctor didn't agree.

What is it that makes mobile phones potentially harmful? The answer is radiation. High- tech machines can detect very small amounts of radiation from mobile phones. Mobile phone companies agree that there is some radiation, but they say the amount is too small to worry about.

As the discussion about their safety continues, it appears that it's best to use mobile phones less often. Use your regular phone if you want to talk for a long time. Use your mobile phone only when you really need it. Mobile phones can be very useful and convenient, especially in emergencies. In the future, mobile phones may have a warning label that says they are bad for your health. So for now, it's wise not to use your mobile phone too often

Most people think that lions only come from Africa. This is understandable because in fact most lions do come from there but this has not always been the case. If we went back ten thousand years, we would find that there were lions roaming vast sections of the globe. However now, unfortunately only a very small section of the lion's former habitat remains.

Asiatic lions are sub-species of African lions. It is almost a hundred thousand years since the Asiatic lions split off and developed as a sub-species. At one time the Asiatic lion was living as far west as Greece and they were found from there, but in a band that spreads east through various countries of the Middle East, all the way to India. In museums now, you can see Greek coins that have clear images of the Asiatic lion on them. Most of them are dated at around 500 B.C. However, Europe saw its last Asiatic lions roaming free two thousand years ago. Over the next nineteen hundred years the numbers of Asiatic lions in the other areas declined steadily, but it was only in the nineteenth century that they disappeared from everywhere but in India.

The Gir Wildlife Sanctuary in India was established especially to protect the Asiatic lion. There are now around three hundred Asiatic lions in India and almost all of them are in this sanctuary. However, despite living in a sanctuary, which makes them safe from hunters, they still face a number of problems that threaten their survival. One of these is the ever-present danger of disease. This is what killed more than a third of Africa’s Serengeti lions in 1994, and people are fearful that something similar could happen in the Gir Sanctuary and kill off many of the Asiatic lions there.

India's lions are particular vulnerable because they have a limited gene pool. The reason for this is interesting is because all of them are descended from a few dozen lions that were saved by a prince who took a particular interest in them. He was very healthy, and he managed to protect them; otherwise they would probably have died out completely.

When you see the Asiatic lion in India, what you sense is enormous vitality. They are very impressive animals and you would never guess that they have this vulnerability when you look at them.

Over the past 600 years, English has grown from a language of few speakers to become the dominant language of international communication. English as we know it today emerged around 1350, after having incorporated many elements of French that were introduced following the Norman invasion of 1066. Until the 1600s, English was, for the most part, spoken only in England and had not extended even as far as Wales, Scotland or Ireland. However, during the course of the next two centuries, English began to spread around the globe as a result of exploration, trade (including slave trade), colonization, and missionary work. Thus, small enclaves of English speakers became established and grew in various parts of the world. As these communities proliferated, English gradually became the primary language of international business, banking and diplomacy.

Currently, about 80 percent of the information stored on computer systems worldwide is in English. Two-thirds of the world’s science writing is in English, and English is the main language of technology, advertising, media, international airports, and air traffic controllers. Today there are more than 700 million English users in the world, and over half of these are non-native speakers, constituting the largest number of non-native users than any other language in the world.

As a result of the recent oil crisis, 9.9 million of California’s 15 million motorists were subjected to an odd – even plan of gas rationing. The governor signed a bill forcing motorists with license plates ending in odd numbers to buy gas only on odd – numbered days, and those ending in even numbers on even – numbered days. Those whose plates were all letters or specially printed had to follow the odd – numbered plan.

Exceptions were made only for emergencies and out – of – state – drivers. Those who could not get gas were forced to walk, bike, or skate to work.

This plan was expected to eliminate the long lines at many service stations. Those who tried to purchase more than twenty gallons of gas or tried to fill a more than half filled tank would be fined and possibly imprisoned.

Computer programmer David Jones earns £35,000 a year designing new computer games, yet he cannot find a bank prepared to let him have a cheque card. Instead, he has been told to wait another two years, until he is 18.

The 16-year-old works for a small firm in Liverpool, where the problem of most young people of his age is finding a job. David's firm releases two new games for the expanding home computer market each month.

But David's biggest headache is what to do with his money.

Despite his salary, earned by inventing new programs within tight schedules, with bonus payments and profit-sharing, he cannot drive a car, take out a mortgage, or obtain credit cards.

He lives with his parents in their council house in Liverpool, where his father is a bus driver. His company has to pay £150 a month in taxi fares to get him the five miles to work and back every day because David cannot drive.

David got his job with the Liverpool-based company four months ago, a year after leaving school with six O-levels and working for a time in a computer shop. "I got the job because the people who run the firm knew I had already written some programs," he said.

"I suppose £35,000 sounds a lot but actually that's being pessimistic. I hope it will come to more than that this year." He spends some of his money on records and clothes, and gives his mother £20 a week. But most his spare time is spent working.

"Unfortunately, computing was not part of our studies at school," he said. "But 1 had been studying it in books and 'magazines for four years in my spare time. 1 knew what 1 wanted to do and never considered staying on at school. Most people in this business are fairly young, anyway."

David added: "I would like to earn a million and 1 suppose early retirement is a possibility. You never know when the market might disappear."

A rather surprisingly geographical feature of Antarctica is that a huge freshwater lake, one of the world's largest and deepest, lies hidden there under four kilometers of ice. Now known as Lake Vostok, this huge body of water is located under the ice block that comprises Antarctica. The lake is able to exist in its unfrozen state beneath this block of ice because its waters are warmed by geothermal heat from the earth's core. The thick glacier above Lake Vostok actually insulates it from the frigid temperature (the lowest ever recorded on Earth) on the surface.

The lake was first discovered in the 1970s while a research team was conducting an aerial survey of the area. Radio waves from the survey equipment penetrated the ice and revealed a body of water of indeterminate size. It was not until much more recently that data collected by satellite made scientist aware of the tremendous size of the lake; satellite -borne radar detected an extremely flat region where the ice remains level because it is floating on the water of the lake.

The discovery of such a huge freshwater lake trapped under Antarctic is of interest to the scientific community because of potential that the lake contains ancient microbes that have survived for thousands upon thousands of years, unaffected by factors such as nuclear fallout and elevated ultraviolet light that have affected organisms in more exposed areas. The downside of the discovery, however, lies in the difficulty of conducting research on the lake in such a harsh climate and in the problems associated with obtaining uncontaminated samples from the lake without actually exposing the lake to contamination. Scientists are looking for possible ways to accomplish this.

Stars have been significant features in the design of many United States coins and their number has varied from one to forty-eight stars. Most of the coins issued from about 1799 to the early years of the twentieth century bore thirteen stars representing the thirteen original colonies. Curiously enough, the first American silver coins, issued in 1794, had fifteen stars because by that time Vermont and Kentucky has joined the Union. At that time it was apparently the intention of mint officials to add a star for each new state. Following the admission of Tennessee in 1796, for example, some varieties of half dimes, dimes, and half-dollars were produced with sixteen starts. As more states were admitted to the Union, however, it quickly became apparent that this scheme would not prove practical and the coins from A798 on were issued with only thirteen stars-one for each ofthe original colonies. Due to an error at the mint, one variety of the A828 half cent was issued with only twelve stars. There is also a variety of the large cent with only A2 stars, but this is the result of a die breakand is not a true error.