【连题】 根据以下资料，回答48~51题。

　　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 out for faults in small steel balls that are being made in one factory.When the pigeon sees a ball which looks different from others, it touches a steel plate with its beak.This turns on a light to warn people in the factory.At the same time a few seeds are given as a reward.It takes three to five weeks to train a pigeon to do this and one pigeon can inspect 3 000 to 4 000 balls an hour.

　　Apes have been used in America in helping to make cars, and scientists believe that these large monkeys may be one day gather crops and even drive trains.

　　第48题 What made scientists think animal can be made to work for us one day?

　　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.

　　【正确答案】：A

　　试题解析：参见句子：They point out that at a circus，for example，we may see elephants，monkeys，dogs and other animals doing quite skillful things.句中they指的就是scientists。

　　第49题 The trainer usually gives the animal a piece of candy or fruit __.

　　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

　　【正确答案】：D

　　试题解析：动物做一个表演，就给它一些吃的东西。

　　第50题 Many animals may be trained to do simple jobs if they know __.

　　A.who their trainers are

　　B.they will be praised by theft trainers

　　C.they will get a reward

　　D.something dangerous will happen to them

　　【正确答案】：C

　　试题解析：参见句子：The scientists say that many different animals may be trained to do anumber of simple jobs if they know they will get a reward for doing them.

　　第51题 Which of the following is not true?

　　A.Scientists consider apes may drive trains some day.

　　B.Apes have worked in some factories.

　　C.Apes may one day be used to gather crops.

　　D.An ape is not a large monkey.

　　【正确答案】：D

　　试题解析：文中最后一段中large monkeys就指apes。