阅读理解。
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 there. In northern Europe, there is a kind of mouse. They leave their mountain homes when
they become too crowded. They move down to the low land. Sometimes they move all the way to the
seaside, and many of them are killed when they fall into the sea.
Recently, scientists have studied the migration of a kind of lobster(龙虾). Every year, when the
season of bad weather arrives, the lobster get into a long line and start to walk across the floor of the
ocean. Nobody knows why they do this, and nobody knows 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 travel.
1. Most animals move from one place to another at a certain time to _____.
A. find food more easily
B. enjoy warmer weather
C. give birth
D. find beautiful places
2. The mice in northern Europe move when _____.
A. they need fresh water
B. the weather is bad
C. the place gets too crowded
D. they haven't enough food
3. This passage is mainly about _____.
A. why animals move from one place to another
B. how animals can find food easily
C. new discoveries of animals traveling
D. some problems with traveling