问题
Hardly _______ to sleep when _______ the door.
A:had I gone；someone knocked at
B:I had gone；did someone knock at
C:had I gone；did someone knock at
D:did I go；someone knocked at
B:I had gone；did someone knock at
C:had I gone；did someone knock at
D:did I go；someone knocked at
正确答案是：
