一、根据句意及所给中文提示、英文解释或首字母，写出句中所缺单词，每空限填一词。
1. When people ride motorbikes, they must wear (头盔).
2. —What do you think of life on (火星)?
—It is interesting, but I don’t want to live there.
3. We may need to wear special boots because of the problem of (重力).
4. The old man can’t breathe smoothly. We should give him an air (a container that holds liquid or gas).
5. D food can be stored for a very long time and doesn’t go bad.

一、1. helmets 2. Mars 3. gravity 4. tank 5. Dried

二、用括号中所给词的适当形式填空。
1. That is the only way I can think of (prove) what I said is true.
2. There will be less (pollute) on Mars than on the earth.
3. I want a (sleep) bag for the coming trip.
4. It’s reported that there’s no fruit (and) vegetables on Mars.
5. We need to wear special boots to make us heavier because there is (little) gravity on Mars.
6. —Do you believe that by 2100 many people (live) on other planets?
—Yes.
7. My brother hated (watch) TV, but now he is a couch potato.
8. —How will you walk on Mars?
—I need (wear) special boots.
9. The students (discuss) what life will be like in the future now.
10. There are many different kinds of fresh and (dry) fruits on sale in that fruit shop.

二、1. to prove 2. pollution 3. sleeping 4. or 5. less 6. will live 7. watching 8. to wear 9. are discussing 10. dried