选择Who，Where， How， How old或How many填空。

1. — _____ is my pencil? 

    — Sorry, I don't know.

2. — _____ apples are there on the tree? 

   — Let me see.

3.— _____ is that boy? 

   — He is my friend, Mike.

4.— _____ are you? 

   — I'm fine. Thank you.

5.— _____ is your sister? 

   — She is nine.