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Can animals be made to work for us Some scientists think that one day animals may be trained to do a number of simple jobs that are now done by human beings.
They point out that at a circus, for example, we may see elephants, monkeys, dogs and other animals doing quite skillful things. Perhaps you have seen them on the television or in a film. If you watch closely, you may notice that the trainer always gives the animal a piece of candy or a piece of fruit as a reward. The scientists say that many different animals may be trained to do a number of simple jobs if they know they will get a reward for doing them.
Of course, as we know, dogs can be used to guard a house, and soldiers in both old and modern times have used geese to give warning by making a lot of noise when a stranger or an enemy comes near. But it may be possible to train animals to work in factories. In Russia, for example, pigeons which are birds with good eyesight, are being used to watch out for f
A. Animals are very skillful at a circus.
B. They are big and strong.
C. Some animals are as clever as human beings.
D. Animals can be trained because they like to get something as a reward.

Can animals be made to work for us Some scientists think that one day animals may be trained to do a number of simple jobs that are now done by human beings.
They point out that at a circus, for example, we may see elephants, monkeys, dogs and other animals doing quite skillful things. Perhaps you have seen them on the television or in a film. If you watch closely, you may notice that the trainer always gives the animal a piece of candy or a piece of fruit as a reward. The scientists say that many different animals may be trained to do a number of simple jobs if they know they will get a reward for doing them.
Of course, as we know, dogs can be used to guard a house, and soldiers in both old and modern times have used geese to give warning by making a lot of noise when a stranger or an enemy comes near. But it may be possible to train animals to work in factories. In Russia, for example, pigeons which are birds with good eyesight, are being used to watch out for f
A. when it is hungry
B. before it plays a trick
C. when it starts to play a trick
D. after it has done the trick

Scientists can learn about man by studying animals, such as mice, rats and monkeys. The scientists in a laboratory are experimenting on mice and they are studying the relationship between diet and health.
In this experiment, the scientists are studying the relationship between the amount of food the mice can eat and their health. The mice are in three groups. All these groups are receiving the same healthy diet. But the amount of food that each group is receiving is different. The first group is eating one cup of food each day, the second two cups, and the third three cups.
After three years, the healthiest group is the one that is only eating one cup of food each day. The mice in this group are thinner than normal mice but they are more active. Most of the day, they are running, playing with one another, and using the equipment in their cages. Also, they are living longer. Mice usually five for two years, while most of the mice in this group are still alive after
A. they run and play all day long
B. they eat only one cup of food a day
C. they live longer than the other groups
D. they are bored with the kind of food in the cup