【题目】They ______ have arrived at lunchtime but their flight was delayed.
A.will
B.can
C.must
D.should

【答案】D
【解析】考查虚拟语气。句意：他们本应该午餐时到达，但是被航班耽误了。本题考查虚拟语气故A、B项排除，must have done“过去肯定做了某事”；should have done“过去应该做某事而实际没做”，故选D。