---Mike must have known that.
---No, he . How he?
A. mustn’t, must
B. may not, might
C. couldn’t, can
D. needn’t, need
网友回答
A. mustn’t, must
B. may not, might
(答案→)C. couldn’t, can
D. needn’t, need
解析：must have done对过去的肯定的推测，否定句用can’t或couldn’t；第二空根据题意他怎么会知道，因此本题选C。