A landing on Mars is within the _____ of current physical theory.

　　A. scheme    B. scope    C. scrap    D. scale

A landing on Mars is within the _____ of current physical theory.

　　A. scheme    B. scope    C. scrap    D. scale

For thousands of millions of years the moon has been going round the earth. At that time, the moon was the 　36 satellite(卫星)of the earth. Today, 　37 , the earth has many other satellites. All of them are 38 by man. These man-made satellites are very much smaller than the moon. However, some of them will still be going 39 the earth thousands of years from now.

Man-made satellites don’t 40 because they are going too fast to do so. As they speed along, they 41 to go straight off into space. They 42 out of the earth, or its gravity, which 43 them from doing this. As a result, they travel in an orbit(轨道)round the earth.

If a man-made satellite travels about at a certain height, it can keep going 44 round the earth, just like the moon. This is 45 it is above the atmosphere(大气), and there is nothing to 46 it down. If it travels 47 than that, it will be slowed down so much that it will 48 the earth.

Men have 49 spaceships to the moon and to the two 50 planets Mars(火星) and Venus(金星). By putting a camera on 51 the spaceship to the moon, men have been able to 52 photographs of the other side of the moon. This side is always 53 from us as the moon 54 the earth. The 55 were later transmitted by radio to the earth. They showed that the other side of the moon is very much the same as the side that turns towards us.

36. A. first　　　　　　 B. second　　　　　　　　　C. last　　　　　　　　　　 D. only

37. A. then　　　　　　B. however　　　　　 　 C. though　　　　　　　　 D. so

38. A. found　　　　　B. discovered　　　　　　C. made　　　　　　　　　 D. sent

39. A. with　　　　　 B. round　　　　　　　　　 C. behind　　　　　　　　 D. after

40. A. fall　　　　　　 B. rise　　　　　　　　　　　　C. break　　　　　　　　 D. stop

41. A. want　　　　 B. wish　　　　　　　　　 C. hope　　　　　　　　　 D. tend

42. A. pull　　　　　 B. push　　　　　　　　　　 C. take　　　　　　　　　　 D. launch

43. A. protects　　B. keeps　　　　　　　　　　C. makes　　　　　　　　 D. discourages

44. A. in and in　 B. on and on　　　　　　 C. out and out　　　　　D. up and up

45. A. because　 B. why　　　　　　　　　　　 C. whether　　　　　　　 D. when

46. A. hand　　　　 B. force　　　　　　　　　 C. slow　　　　　　　　　　 D. bring

47. A. higher　　　 B. longer　　　　　　　　　　 C. more　　　　　　　　　 D. lower

48. A. leave away　　　　　 B. fall to　　 C. go after　　　　　　　　 D. knock over

49. A. gave　　　　 B. offered　　　　　　　　　　C. sent　　　　　　　　　 D. drove

50. A. nearest　　 B. smallest　　　　　　　　　C. biggest　　　　　　 D. closest

51. A. board　　　 B. right　　　　　　　　　　 C. left　　　　　　　　　　 D. top

52. A. form　　　　 B. film　　　　　　　　　　　　C. catch　　　　　　　 D. take

53. A. far　　　　　　　B. hidden　　　　　　　　　C. different　　　　　　 D. separated

54. A. leads　　　　　 B. obeys　　　　　　　　　 C. circles　　　　　　　 D. pursues

55. A. information　 B. letters　　　　　　　　　C. sounds　　　　　　 D. photos

　　Is there life on Mars（火星）? We do not know. But we are sure that earth people do not live on Mars. Earth people need oxygen to breathe. There is almost no oxygen on Mars. It is uncertain exactly how life arose on Earth, so it is difficult to determine how common such mechanisms are. But if life also arose on Mars, this would show that those mechanisms operated not just once, but twice, arguing that life may well be common elsewhere.

　　Living on Mars would be like living on a very high mountain. There would be little air. It might be 50 degree above zero at noon and 100 degree below zero at night.

　　Many people think there may be plants on Mars. We know that Mars has carbon. This is a kind of material found in all plants and animals on earth. Through a telescope, Mars looks red. In some places, it seems gray. At times, the gray colour turns gray--green, then brown, then gray again. The gray-green colour may be a kind of plant life changing colour with seasons.

　　Mars is a spectacular（引人入胜）place, and will remain so even if it is finally proved to be lifeless. Today, we don't know for sure if there is or ever was life on Mars. But one thing is certain--one day, there will be.

　　Will man go to Mars one day? If they do, they will have to take along their own oxygen, food, clothing, and shelter（住所）.

(1)What do you think is the main reason why men can't live on Mars? Because ________ .

[　　]

A．living on Mars is like living on a high mountain

B．here is no oxygen on Mars

C．there are not any plants or animals on Mars

D．on Mars it is too hot at noon and too cold at night

(2)The story does not say this, but from what we have read, we can tell that ________ .

[　　]

A．someday we may know if there is life on Mars

B．men must take food and clothing with them when they go to Mars

C．people on Mars need no air to breathe

D．the plants on Mars are red

(3)The main idea of the whole story is that ________ .

[　　]

A．there may be life on Mars

B．earth people could live on Mars

C．Mars turns its colour with seasons

D．man will one day land on Mars

(4)Which of the following does this story lead you to believe? ________ .

[　　]

A．Some earth people have already visited Mars

B．There is a lot of oxygen and carbon on Mars

C．There may be strange forms of life on Mars

D．Mars is earth people's future home