问题补充：
— Has your mother finished her paper yet?
— I don’t know; she it this morning.
A. wrote
B. has written
C. had written
D. was writing
答案：
A. wrote
B. has written
C. had written
(答案→)D. was writing
解析：考查时态。句意：—你妈妈写完论文了吗？—我不知道，今天早晨她还在写呢！根据句意说明在今天早上这段过去的时间里所发生的事情，所以使用过去进行时。故D正确。
