Run quickly, ________ you'll catch up with others.

[　　]

Run quickly，__________ you'll catch up with others．

　　A．or　　B．and　　C．because　　D．but

Do you know why different animals or insects have their special colors? Colors are used mainly to protect themselves.
Why can’t some birds easily catch locusts（蝗虫）? It is because locusts change their colors together with the change of the colors of crops. When crops are green, locusts look green. But as autumn comes, locusts change to the same brown color as crops have. Some other insects with different colors from plants are easily found and eaten by others. So they have to hide themselves for lives in the day 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 can’t be easily seen by hunters. This is because they have the colors much like the trees.
Have you ever noticed an even more strange thing? A kind of fish in the sea can send out black liquid when it faces danger. While the liquid spreads over, its enemies can’t find it. And it quickly swims away. So it has lived up to now though it is not strong at all.
【小题1】 From the article we learn that locusts 　　　　　　　　　.

Do you know why different animals or insects have their special colors? Colors are used mainly to protect themselves.

Why can’t some birds easily catch locusts（蝗虫）? It is because locusts change their colors together with the change of the colors of crops. When crops are green, locusts look green. But as autumn comes, locusts change to the same brown color as crops have. Some other insects with different colors from plants are easily found and eaten by others. So they have to hide themselves for lives in the day 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 can’t be easily seen by hunters. This is because they have the colors much like the trees.

Have you ever noticed an even more strange thing? A kind of fish in the sea can send out black liquid when it faces danger. While the liquid spreads over, its enemies can’t find it. And it quickly swims away. So it has lived up to now though it is not strong at all.

1. From the article we learn that locusts 　　　　　　　　　.

A. are dangerous to their enemies           B. are easily found by birds

C. change their colors to protect themselves   D. are small animals

2.How can insects with different colors from plants keep out of danger?

A. They have to move quietly.

B. They hide themselves in the day and appear at night.

C. They have the colors much like their enemies.

D. They run away quickly.

3. Bears and lions can keep safe because 　　　　　　　　　.

A. they live in forests                  B. they like brown and grey colors

C. they move quietly　                   D. they have the colors similar to the trees

4.What does the word “liquid” mean in the last paragraph?

A. 气体          B. 固体　       C. 液体　       D. 水蒸气

5. Which is the best title for this passage?

A. The Main Use of Colors for Animals and Insects

B. Colors of Different Animals and Insects

C. The Change of Colors for Animals and Insects

D. The Change of Different Animals and Plants