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

问题描述:

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?

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.