用must, might, could和can't完成对话
A: Tina, you look worried. What's wrong ?
B : I (1) ________ find my English book. I (2) ________ have lost it .
A: Don't worry. Let's see where it (3) ________ be.
B: I think I (4) ________ leave it in the reading-room. But it isn't there.
A: What's your book look like.? Let's look for it together.
B : It's blue.
A: Oh, Look! Is this one yours?
B: No. It (5) ________ be mine. Tom's name is on it.
A: I'm afraid you have to buy a new one.