- Do you know where my address book is?　　　　- It be in the hall cupboard. I think I saw it

问题补充：

- Do you know where my address book is?

- It be in the hall cupboard. I think I saw it this morning.

A. could

B. can

C. will

D. must

答案：

(答案→)A. could

B. can

C. will

D. must

解析：could表示过去的推断，后句中的saw已提示。