As space science develops, man has learned more and more about space. Space is not only amazing but also dangerous. While working in space, spacemen are facing danger as well as success.

   Scientists have found out that the radiation（辐射） is the greatest danger to spacemen in space. When spacemen are working in space, they are in danger of the radiation from the sun and other stars, which is bad for their health. The harm of the radiation won’t be found until their children even grandchildren are born. Some special medicine may work a little, but no really effective medicine has been found so far.

   Space rubbish is also thought to be a great danger to spacemen. It’s reported that there were 9,000 man-made things flying in space. About 30% of these are satellites, 10% are spaceships, and the rest are space rubbish. An explosion（爆炸）in space in 1999 made a cloud of 300,000 fragments, each at least 4mm in size. A small piece of these even knocked a spaceship window and caused some damage.

   Scientists are watching and reporting any possible danger all the time. They are working to deal with space rubbish. Although space is really dangerous, it interests many people on the earth. In the near future, it may become possible for people to spend a few days in a space hotel. We may even choose to leave the earth and live in space in a few years. So we should do something to help improve the space environment.

51. ______ shows the man-made things in space in the correct way.

A.                               B.                           C.                       D.

52. The radiation from the sun and other stars is ______ to spacemen.
A. good   B. helpful   C. useful  D. harmful

53. The underlined word “fragments” means “______”.
A. pieces   B. foam   C. smog   D. UFOs

54. The passage talks about _________ kinds of danger in space.
A. two   B. three      C. four     D. five

55. Which of the following is TRUE?
A. Scientists have found out ways to solve any problem in space.
B. Every one of us can have a travel to space in ten years.
C. The harm of the radiation may be found in the spacemen’s children.
D. Space is really dangerous, so it doesn’t interest anyone on the earth.

    When you look at the sky at night, the moon looks bigger than the stars. Actually, the moon is much smaller than the stars and the sun. It's much smaller than the earth. But the moon is much close to us than any star.  hat is why it looks so big. If you hold a coin close to your eye, it looks big. If you look at it across the moon, it looks small.

    The moon moves around the earth. It makes one trip in about four weeks. The moon looks flat to us. But it is a round ball, like the earth.

    People once thought the moon had fire on it. They thought the fire made it bright. Now we know the moon is like a mirror. It gets its light from the sun.

    Our sunlight comes from the sun, too. What is the sun? The sun is a star. The stars we can see have their own light. There are many big stars we cannot see. Their light had burned out.  Others are still bright, but they are so far away that we cannot see them. The sun looks bigger and much brighter than other stars because it is the nearest of all stars. The sun and the other stars we see are very hot, but the air around us saves us from the heat of the sun.

    The sun gives us light and warmth. It makes plants grow and turns leaves green. It makes life possible on our earth. It is a life giving star.

52.  It takes_______ for the moon to go around the earth.

    A. more than a week          B. nearly a month

    C. half a year                D. more than a year

53. The moon is bright because_______.

    A. there is some fire on it      B. it is near the sun, too

    C. there is a big mirror on it    D. it can get light from the sun

54.  The passage tells us_______.

    A. the sun is not the biggest star    B. the sun is bigger than any other star

    C. only the sun can shine          D. the sun is one of the farthest stars to us

55.  Why do we call the sun "a life giving star"?

    A.  Because it gives us warmth.

    B.  Because there are some living things on it.

    C.  Because plants and animals can't live without it.

    D.  Because people have to live in the dark without it.