What a pity! I in Hainan two more days，but something urgent needed to be dealt with back home.
A. must have stayed
B. needn't have stayed
C. may have stayed
D. could have stayed
网友回答
A. must have stayed
B. needn't have stayed
C. may have stayed
(答案→)D. could have stayed
解析：must have done对过去发生的事情的肯定推测，只用于肯定句；needn't have done“本不需要做某事，结果做了”；may have done对过去发生的事情的语气不是很肯定的推测，只用于肯定句；can have done用于肯定句意思是“本来能够做某事，但是没做”；用于否定句和疑问句表示对过去发生的事情的推测。由句意可知要用D项。