根据句意，用括号中所给词的正确形式填空。

1. Mr King learned Chinese as his _________ (two) language.

2. If you do your homework _________ (care), you will lose the exam again.

3. We should think about what we can do _________ (keep) animals and plants from becoming endangered.

4. —Did you go to Tom's birthday party? —No, I _________ (not invite)

5. We should do something to stop sandstorms from _________ (happen)

6. The man has known a lot of Chinese since he _________ (come) to China three years ago.

7. They _________ (not go) to the market until they finish their work.

8. The policeman said that he _________ (see) a Young Pioneer help an old woman cross the road

    the day before.