根据首字母提示或括号内的汉语意思拼写单词。

1. Astronauts in flight must a_____ to weightlessness.

2. Don't soil the carpet with your m_____ shoes.

3. His nationality isn't _____ (有关的) to whether he is a good lawyer.

4. I'm not feeling very well today, o_____ I would do it myself.

5. We are expected to p_____ actively in English class.

6. I see them about once a_____ (两周).

7. He presented a new_____ (概念) of the beginning of the universe.

8. We have already made a_____ for our vacation.