Do you know why different animals or pests(昆虫) have their special colors? Colors in them seem to be used mainly to protect themselves.

　　Some birds like eating locusts(蝗虫), but birds cannot easily catch them. Why? It is because locusts change their colors together with the change of the colors of crops(庄稼). When crops are green, locusts look green. But as the harvest time comes, locusts change to the same brown color as crops have. Some other pests with different colors from plants are easily found and eaten by others. So they have to hide themselves for lives and appear only at night.

　　If you study the animal life, you'll find the main use of coloring is to protect themselves. Bears, lions and other animals move quietly through forests. They cannot be easily seen by hunters(猎人). This is because they have the colors much like the trees.

　　Have you ever noticed an even stranger act? A kind of fish in the sea can send out a kind of very black liquid(液体)when it faces danger. While the liquid spreads over(散开), its enemies(敌人) cannot find it. And it immediately swims away. So it has lived up to now though it is not strong at all.

 (    )46．How can pests with different colors from plants keep out of danger?

　　A. They run away quickly.

　　B. They have the colors much like their enemies.

　　C. They hide themselves by day and appear at night.

　　D. They have to move quietly.

(    )47．Bears and lions can keep safe because______.

　　A. they have the colors much like the trees　　 B. they move quietly

　　C. they like brown and gray colors       　　D. they live in forests

 (    )48．Which is the best title for this passage?

　　A. The Change of Colors for Animals and Pests

　　B. Colors of Different Animals and Pests

　　C. The Main Use of Colors for Animals and Pests

　　D. Some Animals and Pests