完形填空

　　It is interesting how NASA(美国航空航天管理局)chose their astronauts(宇航员)for landing them on the moon. They chose men 1 the age of twenty and thirty－five. There were about fifty of them. Many were 2 air pilots. 3 were scientists with two or three degrees. NASA telephoned each man they were going to choose; told him the plans and the 4 they might get in. They then asked him if he was willing to be trained as an astronaut. “How could any man 5 such an exciting job?” One of them said, “Dangerous? Of course, it's dangerous, 6 most exciting!”

　　The health and physical condition of 7 was, of course, very necessary. 8 1 those in very good health and physical condition were chosen.

　　While being trained to be astronauts, they went through many 9 . They studied the stars and the moon, and they also studied geology, the science of rocks. This was necessary 10 astronauts would have to look for rocks on the moon. They would try to find rocks which might help to tell the 11 of the moon. They were all 12 to fly in helicopters. These helicopters landed 13 down to give them some experience of the way the spaceship would 14 land on the moon. They were also taught all the 15 facts about the conditions in. They learnt all the technical details of the spaceships and rockets. They visited the scientists and engineers who 16 them. They visited the factories where they were 17 . They learnt how every 18 of a spaceship and its instruments work. They also learnt every detail of ground－control 19 .

　　In a word, to be chosen as an astronaut, one must be in good health, 20 in science and good at piloting.

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