问题补充：
He at the meeting this morning.He was in hospital at the time.
A. couldn’t have spoken
B. mustn’t have spoken
C. shouldn have spoken
D. needn’t have spoken
答案：
(答案→)A. couldn’t have spoken
B. mustn’t have spoken
C. shouldn have spoken
D. needn’t have spoken
解析：作“不可能”一类的否定推测,不要用mustn’t,而要用couldn’t.
