单选题 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 get away form places that are too corwded.
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. 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 lobsters 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 to travel.

单选题 The majority of animals migrate for?______.
A. place B. safety C. Food D. warmth

单选题 Salmon is known as a creature spending most of its life in ______.
A. they are short of food B. there is not enough space
C. it's getting warmer in the low land D. it's getting coldier in the mountains

单选题 The reason why the lobsters migrate is ______.
A. the bad weather B. the depth of the ocean C. scientist' lack of interest D. unkown

单选题 The passage is mainly about ______.
A. living things on the move B. the most famous migration C. mice in northern Europe D. migration of lobsters