Has he finished his homework yet?Yes,he _____ it an hour ago.

问题描述:

Has he finished his homework yet?Yes,he _____ it an hour ago.
A has done B did C had done D was doing 选哪个?为什么?

B
问某人是否做过某事/某事是否已发生【现在完成】
问某事何时发生的用一般过去时,夲句后面有an hour ago一般过去时的标志.