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阅读下面短文并回答问题，然后将答案写到答题卡相应的位置上。请注意词数要求。

On October 15, 2003, Shenzhou V spaceship was sent into space successfully. Yang Liwei became the first Chinese astronaut to go into space.

It was said that the only object on the earth that could be seen from space was the Great Wall. Yang Liwei also wanted to prove（证实）whether this was true or not. To his disappointment, he couldn’t see it. From space, he tried several times to look for the Great Wall, but he failed. In fact, from space, astronauts can’t see any specific（具体的）object on the earth.

He also saw something cotton-like flying outside of the window. He didn’t know what it was. Maybe it was space rubbish.

There was another strange thing. That was the knock on the spaceship. It appeared once in a while. It sounded like someone outside was knocking on the spaceship, but nothing dangerous happened. So he told the following astronauts not to be afraid. Later when Shenzhou VI and Shouzhou VII were flying in space, this knock came again. But the astronauts on them were not nervous.

Could the knock come from the aliens? Do you want to know the answers?

1．When did Yang Liwei first go into space? (no more than 4 words)
2．What did Yang Liwei try to look for from space? (no more than 3 words)
3．What might the cotton-like thing be? (no more than 2 words)
4．Why did Yang Liwei tell the following astronauts not to be afraid of the knock? (no more than 5 words)
5．How many spaceships are talked about in the passage? (no more than I word)