In the nineteenth century, composer Steven Foster wrote some of the most enduringly popular of all American songs, (4)_________ soon became part of the folk tradition.

Many species of animals are threatened, and could easily become (2)________ if we do not make an effort to protect them. In some cases, animals are hunted for their fur or for other valuable parts of their bodies.

Farmers use powerful chemicals to help them to grow better crops, but these chemicals pollute the environment and (4)________ wildlife.

The most successful animals on earth - human beings - will soon be the only ones (5)________, unless we can solve this problem.

Trees are among the biggest and longest-living things on Earth, some dating back longer than the oldest buildings. But (1)_______ being nice to look at, trees also play an important role in improving the quality of our lives. On a world-wide (2)_______, forests help to slow down the effects of global warming by using up the gas known as carbon dioxide and giving (3)_______ the oxygen we need to breathe. At local neighborhood level, trees also (4)_______ important environment benefits. They offer shade and shelter, which in (5)_______ reduces the  amount of energy needed to heat and cool nearby buildings; at the same time, they also remove other impurities from the air we breathe.

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 (1)_____ 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 (2)_____ 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 (3)_____ of cleaning and carrying jobs and also has to cope (4)______ all the different shapes and positions of rooms, furniture, ornaments, cats and dogs. (5)______ , 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 softwarethe programs that will operate the machine.

A housework robot on the other hand, has to do several different (3)_____ of cleaning and carrying jobs and also has to cope (4)______ all the different shapes and positions of rooms, furniture, ornaments, cats and dogs.

(5)______ , 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 softwarethe programs that will operate the machine.