—Where did you get this book?—I picked it up from a second-hand bookshop if you know.A. m

问题补充：

—Where did you get this book?

—I picked it up from a second-hand bookshop if you know.

A. must

B. will

C. can

D. shall

答案：

(答案→)A. must

B. will

C. can

D. shall

解析：A. must必须，一定 B. will将要 C. can能够 D. shall将要；句意：你从哪里得到这本书的？如果你一定要知道的话，我是从二手书店买的。故选A