Passage Two
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 modem 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
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
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