选择适当的词填空，使句意完整。

1. I can't _____________ (see, sea) anything.

2. This _____________ (pear, pair) of shoes is too cheap.

3. Many _____________ (child, children) like playing with snow.

4. _____________ (There, Their) are some knives.

5. She _____________ (has, have) a good friend at school.

6. We are going to _____________ (buy, bought) a dictionary tomorrow.