If you are in town in a western country, you will often see people walking with their dogs. It is still true that a dog is the most useful animal in the world, but the reason why one keeps a dog has changed. Once upon a time, a man met a dog and wanted it to help him in the fight against other animals, and he found that the dog listened to him and did what he told it to. Later people used dogs for the hunting of other animals, and the dogs didn't eat what they got until their masters agreed. So dogs were used for driving sheep and guarding chickens. But now the people in the towns and cities do not need dogs to hunt other animals. Of course they keep them to frighten thieves, but the most important reason is that people feel lonely in the city. For a child, a dog is his best friend when he has no friends to play with. For a young wife, a dog is her child when she doesn't have her own. For old people, a dog is also a child when their real children have grown up and left. Now people do not have to use a dog but they keep it as a friend, just like a member of the family.
17. In town in a weatern country, dogs are often seen to ________.
A. walk with hunters
B. walk with their masters
C. fight against other animals
D. play with other animals
18. Which of the following is NOT true according to the passage?
A. People used to keep dogs to protect their house birds.
B. Dogs were used to hunt other animals.
C. Dogs will eat what they've got.
D. Dogs can perhaps drive thieves away.
19. The main reason why people in towns and cities raise dogs now is that ________.
A. they want dogs to frighten thieves for them
B. they use dogs for the hunting of other animals
C. they train dogs to drive sheep
D. they want to keep the dogs as friendly members of their families
20. The sentence "Now people do not have to use a dog" means ________.
A. a dog is not as useful as it was before
B. that it isn't necessary for people to use dogs to serve them
C. it isn't necessary for people to keep dogs any longer
D. people don't feel lonely now