Question

Have you found your book yet? - No, I’m not sure ______ I could have left it.

Have you found your book yet? - No, I’m not sure ______ I could have left it. A. whether B. where C. when D. why 为什么？

Answer 1

选择B。此题可以根据意思来进行判断，该句话
主谓宾
都是全的，只能是状语，而根据意思强调是我不知道把它放在哪里了。所以应该选择答案where。

Answer 2

A
只能填if/whether
A意思是是否
B意思是哪里
C意思是何时
D意思是为什么
所以选A

Answer 3

表推断的虚拟语气过去时态的用could
have
done,
打字不易，如满意，望采纳。