--Have you found your book yet? --- No I’m not sure where I it?A. leaveB. had leftC. coul

问题补充：

--Have you found your book yet?

--- No, I’m not sure where I it?

A. leave

B. had left

C. could have left

D. was to leave.

答案：

A. leave

B. had left

(答案→)C. could have left

D. was to leave.

解析：本题考查时态。根据句意：——你还没有找到你的书？没有，我不确定我能够把它丢哪儿了。故用could have done本能够做，选C。