When you take a walk in any city, you often see a lot of people walking dogs. It is still true that a dog is the most useful and faithful animal in the world, but the reason why people keep a dog has changed. In the old days people used to train dogs to protect(保护) themselves against attacks by other beasts. Later they came to realize that a dog was not only useful for protection but willing to obey his master. For example, when people used dogs for hunting, the dogs would not eat what was caught without permission.

These days people in the city need not protect themselves against attacks from animals. Why do they keep dogs, then? Some people keep dogs to protect themselves from robbery（抢劫）. But the most important reason is for companionship. For a child, a dog is a best friend when there are no friends to play with. For young couples, a dog is their child when they have no children. For old couples, a dog is also their child when their natural children have grown up. So the main reason why people keep dogs has changed from protection to friendship.

67. According to the passage, in the old days people trained dogs ______ .

for protection against robbery

just for fun

for companionship

for protection against other animals

68. The word "companionship" may mean ______ .

A. native     B. advice     C. friendly relationship（关系） D. usage

69. The dogs were used for hunting because ______ .

A. they were good hunters

B. they obeyed their masters

C. they were useful for protection

D. they did not eat other animals

70. The most important reason for people to keep dogs now is they ______ .

A. need companion

B. like children

C. enjoy hunting

D .want to protect themselves

71. We can infer from the passage that ______ .

A. dogs can be helpful to those who need company

B. city people always feel lonely

C. dogs can be boring （厌烦的）

D. the city can be a very dangerous place