—Why did you leave without a word of warning to John?
—But what _____ otherwise? He never listens to me.
A．could I have done
B．would I do
C．must I have done
D．should I do
答案：A
题目分析：句意：--为什么你没有留下一句话就离开了？--但是要不我能做什么？他也不听我的。根据第一句可知这里他的离开发生在过去，故用情态动词+have done，所以排除BD；must have done不能用在疑问句中，故选A。
点评：本题难度适中。情态动词的完成式是高中阶段的重难点之一，需要考生熟记它们的用法，在各类考试中经常出现，它主要用于表示对过去情况进行推测或责备等。
即学即练： --- There were already five people in the car but they managed to take me as well.
--- It ___ a comfortable journey.
A. can’t be B. shouldn’t be C. mustn’t have been D. couldn’t have been
解析：D。They were already five people in the car, but they managed to take me as well.一句中的时态，应该是对过去情况的推测判断，因为车上已经有5位人了，在带上我一个，可以断定这一定是一次不舒适的旅行。所以，本句表达的是对过去否定的推测判断，应该用can’t/ could have done来表达。故答案选D。