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 ____ .