1. 方框中选择适当的单词完成句子

their ,  where,  under,  bookcase,  know

1. （1） — is the pencil?

   —It's on the desk.

3. （2） —What's his name?

   —Sorry, I don't ．

5. （3） —Are your keys in your parents' room?

   —Yes, they are on bed.

7. （4） Look! The baseball is the chair.

9. （5） My books are in the .