一个小孩在结冰的河面上玩耍，突然发现脚下的冰层即将要破裂，他_爱下问搜题

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问题选择题

一个小孩在结冰的河面上玩耍，突然发现脚下的冰层即将要破裂，他应（　　）

A．立即站着不动，大声呼叫

B．改成单脚站立，减小压力

C．轻轻伏在冰面，爬向岸边

D．加快速度跑开，逃离冰面

答案

保护一个物体时，一定要减小压强．一个小孩在结冰的河面上玩耍，突然发现脚下的冰层即将要破裂，此时要保护冰不破裂，一定要减小压强，此时不能改变物体的压力，只能增大受力面积，来减小压强．

故选C．

完形填空

The elephant is the biggest four-legged animal in the world. It’s also, perhaps, the gentlest ,   1 not always.
Elephants are like us in some ways. They   2  for a long time—fifty or sixty years. They can 3  things very well. They never forget great sadness or happiness. A female elephant   4 , her daughters and her granddaughters are sad for many months. They stay with the dead   5 . Then they carry a bit of it away with them. They never forget a 6 friend.
Elephants are like us, but they’re also 7 .They live in families; families or females. There will be a few young males-a few “baby boy”. But they will soon be   8 away by their mothers or sisters. An elephant family   9  only its daughters, mothers and grandmothers and its great grandmothers.
The females stay together for fifty, sixty or a hundred years.The older animals   10 the young ones. The mothers teach their daughters and set a good example.And   11  happens to male elephant? Well, the young males stay with their mothers for a time. Then they must   12 the family. The females just send them away. A bull elephant does not often have a friend ,He lives 13 ,away from the family, and away from other bulls.
Sometimes the females call a bull. He can   14 _them then, and they stay for a time. But soon his “wives” and “sisters” send him away again. The females have a very   15
family life. What do the bulls think about it? We don’t know.

名词解释

鱼类群体