Do you know why different animals or pests have their special colors? Colors in them seem to be mainly used to protect themselves.
Some birds like eating locusts (蝗虫), but birds cannot easily catch them. Why? It is because locusts change their colors with the change of the colors of crops. When crops are green, locusts look green. But as the harvest time comes, locusts change into the same brown color as crops have. Some other pests whose colors are different form 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 animals’ life, you’ll find the main use of colors is to protect themselves. Bears, lions and other animals move quietly through forests. They cannot be easily seen by hunters because their colors are much like the trees.
Colors are useful not only on the land, but also in the sea. A kind of fish in the sea can give out a kind of black liquid (液体) when the fish face danger. The liquid spreads over quickly, so they cannot be found by their enemies and can quickly swim away. That is why they live safely though they are not strong at all.
From the passage, we can know that ________.

A．locusts are big animals

B．Locusts are easily found by birds

C．Locusts are dangerous to their enemies

D．Locusts can change their colors to protect themselves

Those pests with different colors from plants have to ________ to keep out of danger.

A．change their colors

B．hide in the day time and appear at night

C．move quietly

D．hide at night and appear in the day time

Bears and lions can keep safe because _______.

A．their colors are much like the trees

B．they move quickly

C．they are very strong

D．they live in forests

According to the passage, the fish can keep safe because ________.

A．they can change their colors

B．they can give out a kind of liquid

C．they are strong enough

D．they swim faster than any other fish

Which is the best title for this passage?

A．The colors of the seasons

B．Animals on the land and in the sea

C．The main use of colors for animals and pests

D．How to keep safe in the sea