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Mars?

A. The meteorite containing organic compounds is part of Mars.

B. A Martian rock struck Earth about 11,000 years ago.

C. The organisms came back to life after the collision with Earth.

D. The inhabiting organisms appeared more than three billion years ago. 40. How many arguments in this passage lead to the belief of the existence of life on Mars?A. Two. B. Three. C. Four. D. Five. Passage 3

Have you ever wondered why different animals or pests have their particular colors? Colors in them seem to be used mainly to protect themselves.

Birds, especially seagulls, are very fond of locusts, but birds cannot easily catch locusts because locusts change their colors together with the change of the color of crops. When crops are green, locusts look green. But when crops are ripe, locusts take on exactly the same brown color as crops have. Some other pests with different colors from plants are usually easily found and eaten by their enemies. So they have to hide themselves in terror for lives and appear only at night.

If you study the animal life in any part of the world, you will find the main use of coloring is to protect themselves. Bears, wolves and other beasts move quietly through forests. They are usually invisible to the eyes of hunters, because they have the color much like the barks of trees.

An even more strange act remains to be noticed. A kind of fish living in seas can send out a kind of very black liquid when it faces danger. While the liquid spreads over, its enemies cannot find it, and it immediately swims away. Thus, it has existed up to now though it is not powerful at all.

41. This passage mainly talks about ______. A. the change of color in locusts

B. the protective coloration of animals and pests

C. how a certain sea fish protects itself

D. animals or pests can dye themselves different colors

42. Locusts are not easily wiped out by their enemies because ______. A. they are powerful enough

B. they are dangerous to their enemies

C. they take on the same colors as crops

D. they fly extraordinarily fast

43. The pests that have different colors from plants usually appear at night

because ______.

A. birds take their rest when night comes

B. their enemies can easily find them and eat them

C. they have the habit of coming out in darkness

D. it’s easy for them to destroy plants in darkness