Complete the sentences with the given words in their suitable forms. (用所给词的正确形式填空)

1. I think there _______ (be) fewer trees next year.

2. He              (collect) 300 pictures since 5 years ago.

3. Sam always              (help) his classmates last term.

4. Would you mind _______ (play) games after school?

5. My father came into the bedroom while I _______ (dance).

6. If you want to cross a street, you _______ (wait) for the green light.

7. American fast food seems _______ (be) the most popular in the world.

8. They ______ (eat) a lot of potatoes yesterday, so did I.

9. My mother made me              (clean) my room all by myself yesterday.

10. Please look carefully before you _______ (cross) the street.