单词拼写。

1. He was interested in a _____ and always stayed up at  night to watch the stars.

2. Computer hackers have broken down security s ____,  raising questions about the safety

    of information.

3. There is a lot of rubbish ____(漂浮)on the surface of the river.

4. W _____(当心 )out! There is a car coming!

5. Every time an English runner won a race, the crowd c  ____  .