Question

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

I’m not sure where I ______ it? - No.leave B.had left C.could have left. DHave you found your book yet. A

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

本来我不看答案会用left，因为是过去。所以could
have
done
表示对过去的可能性。
例如：The
ground
was
wet
so
it
must
have
rained
last
night.