There is no light in the dormitory. They must have gone to the lecture,_____?There is no light in the dormitory. They must have gone to the lecture,_____?A.didn’t theyB.don’t theyC.mustn’t theyD.haven’t theyThe key is DWhy not b

熱心網友

B.don’t they是一般現在時,D.haven’t they是現在完成時,因為說話時他們去圖書館還沒回來.而且They must have gone 中的must表推測,句子主干是they have gone 所以后面反意疑問句應和have gone對應.所以用haven’t they.

熱心網友

must have done 表推測當起主句表示現在時態時用ＨＡＶＥ．．．當其主句表示過去時態時用ＤＩＤ．．．