Student: We all went to see that movie.
Teacher: But the sign says that the movie is for adults only. You _____ admitted.
(A) aren't to be
(B) hadn't have been
(C) mustn't have been
(D) shouldn't have been
【Mary Hong】評論
這部電影是給成人以上年紀的人觀賞，你不應該被允許進入觀看。事情已經發生(學生看了電影)，所以要用 (D) shouldn't have been
【Last Night Wo】評論
但是C為何不可
【Hsu Baleng】評論
must + have + p.p. + 過去時間副詞，表對過去的推測，意為「過去一定」shouldn't have p.p.則表示"你不應該這樣做 你卻這樣做了"