4．
根据短文内容，选择正确答案填空。 Many people have the wrong ideas about pigs. Pigs are actually(买际上) very clean animals. On farms, they live in dirty places, so they become very dirty. But in the wild, pigs keep themselves very clean.
They are also very smart. They may he smarter than clogs. So pigs can learn things from people.
Pigs are very friendly animals. Some people raise (饲养) them as pets. Of course, people raise the smart kind, not the big kind. Small pigs are very cute. And they don't break things in the house. Big pigs usually live outside on the farms, not in people's houses.
