【题目】My son ____ the examination, but he wasn't careful enough.
A. might be able to pass B. must have passed
C. could have passed D. were able to pass
在线课程【答案】C
【解析】
试题分析：考查虚拟语气。句意：他本来能够通过考试，但是他不够细心。“would+have+done”表示对过去事情的假设，表示本来会做而没有做的动作。联系句子意思可知选C。