一则故事：以前有一支旅行队，当一切置办齐全时，队长发现还缺少两样东西，于是他大声叫到：“我们还缺少一个犹太人和一条狗。”一个犹太人听到了，便回敬道：“我和你一起，不就齐全了吗？！”

    When you take a walk in any of the cities in the West, you can see a lot of people ____(walk) with dogs. It is still true that a dog is the most useful and faithful animal in the world, but the reasons why people keep a dog ____(change). In the old days people used to train dogs to protect themselves against attacks by other beasts. And ____(late) they came ____(realize) that a dog was not only useful for protection,____ willing to obey his master. For example, when people used dogs for hunting, the dogs would not eat what was caught without ____(permit). But now people in the city need not protect themselves against attacks of animals. Why do they keep dogs, then? Some people keep dogs to protect themselves from robbery. But the ____(important) reason is for companionship. For a child, ____ dog is his best friend when he has no friends to play with. For young couples, a dog is ____child when they have no children. For old couples, a dog is also their child when their real children have grown up. So the main reason why people keep dogs has changed from protection ____ friendship.