填入所缺的词完成对话，一空一词。
A: Look！What’s that under the tree?
B: Let’s have a look. Oh, it’s a __1__.
A: __2__does the backpack belong __3___?
B: I __4___ know. Let’s open it. Look here! It ___5___ be a girl’s because there is a red T-shirt.
A: Well, it could ___6___ a boy’s. The red T-shirt might be a present ___7___ his sister.
B: Hey, I know ___8___ backpack it is.
A: Really? Who is the ____9___ of it?
B: It must be Pierre’s. The T-shirt has his name ___10___ it.
1. backpack 2. Who 3. to 4. don’t 5. might
6. be 7. for 8. whose 9. owner 10. on