Do you know why different animals or pests have their special colours? Colours 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 colurs with the changes of the colours of crops .When crops are green, locusts look green .But as the harvest time comes, locusts change into the same brown colour as crops have .Some other pests whose colours are different 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 animals’ life, you’ll find the main use of colours is to protect themselves .Bears, lions and other animals move quietly through forests .They cannot be easily seen by hunters because their colours are much like the trees.
Colours 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 can 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 colours to protect themselves

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

A．change their colours

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 colours 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 colours

B．they can give out a kind of black liquid

C．they are strong enough

D．they swim faster than any other fish

Which is the best title for this passage?

A．The colours of the seasons

B．Animals on the land and in the sea

C．The main use of colours for animals and pests

D．How to keep safe in the sea