what you when your mother came back?A.are;doing B.were;doing C.did;do D.was;doing

问题描述:

what you when your mother came back?
A.are;doing B.were;doing C.did;do D.was;doing

答案是 B.were;doing
when your mother came back 当你的妈妈回来,这是过去完成时态,因此前面的动作是过去正在进行时态