Can we make animals work for us? Some scientists think that one day we can teach animals to do a lot of things for people. They say that in a film or on TV you may see elephants, monkeys, dogs or some other animals doing a lot of things. If you watch carefully, you may find those animals are always given a little food to eat after they have done something. Scientists say that people can teach many different animals to do some easy work if they know they will get something to eat.               We all know elephants can carry large logs  and dogs can look after houses. And we can even teach animals to work in factories. In America, for example, people use apes to help make cars. Scientists think that those big monkeys may, one day, drive trains. Now people are trying to let them do something just like man. People can teach animals to do some easy work if  _  .
the animals have enough food to eat the animals learn they'll get something to eat the animals are as clever as man the animals are big enough.