12．
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（輻射） 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 9，000man-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 1999made 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．
53．B shows the man-made things in space in the correct way．
54．The underlined word"fragments"means"B"．
A．泡沫
B．碎片
C．煙霧
D．飛碟
55．Which of the following is TRUE？C
A．Every one of us can have a travel to space in ten years．
B．Scientists have found out ways to solve any problem in space．
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．
