问题补充：
We know that many animals do not stay in one place. Birds,fish and other animals move from one place to another at a certain time. They move for different reasons: most of them move to find food more easily,but others move to get away from places that are too crowded.
When cold weather comes,many birds move to warmer places to find food. Some fishes give birth in warm water and move to cold water to feed. The most famous migration（迁移）is probably the migration of the fish which is called “salmon”.This fish is born in fresh water but it travels many miles to salt water.There it spends its life. When it is old,it returns to its birthplace in fresh water. Then it gives birth and dies. In northern Europe, there is a kind of mouse. They leave their mountain homes when they bccome too crowded. They move down to the low land. Sometimes they move all the way the seadide,and many of them are killed when they fall into the sea.
Recently, scientists have studied the migration of kind of lobster（龙虾）.Every year, when the season of the bad weather arrives, the lobsters get into a long line and start to walk across the floor of the ocean. Nobody knows why they do this, and nobody know where they go.
So,sometimes we know why humans and animals move from one place to another,but at other times we don’t. Maybe living things just like to travel.
【小题1】.Most animals move from one place to another at a certain time to
A.give birth B.enjoy warmer weather C.find food more easily
【小题2】The fish called “salmon”spends a long time in
A.salt water B.rivers C.fresh water
【小题3】The mice in northern Europe move when
A.they give birth B.the place gets too crowded
C.they haven’t enough food
【小题4】 The lobsters move.
A.to the fresh water B.at a certain time C.to find more food
【小题5】What is the main idea of the passage?
A.Animals move to find food more easily.
B.The migration of the fish called“salmon”is the most famous migration.
C.Sometimes we know why and how living things move from one place to another,but sometimes we don’t.C【小题2】A【小题3】B【小题4】B【小题5】C
答案：
(答案→)C【小题2】A【小题3】B【小题4】B【小题5】C
解析：【小题1】根据第一段第三句“They move for different reasons: most of them move to find food more easily”知答案应选C。
【小题2】根据第二段第三、四和五句“The most famous migration（迁移）is probably the migration of the fish which is called “salmon”.This fish is born in fresh water but it travels many miles to salt water.There it spends its life.”知答案应选A。
【小题3】根据第二段第八和第九句“In northern Europe, there is a kind of mouse. They leave their mountain homes when they bccome too crowded.”知答案应选B。
【小题4】根据第三段第一、二句“Recently, scientists have studied the migration of kind of lobster（龙虾）.Every year, when the season of the bad weather arrives, the lobsters get into a long line and start to walk across the floor of the ocean.”知答案应选B。
【小题5】根据文章最后一句知答案应选C。
