David did not regret saying what he did but felt that heit differently.A. could expressB.

问题补充：

David did not regret saying what he did but felt that heit differently.

A. could express

B. would express

C. could have expressed

D. must have expressed

答案：

A. could express

B. would express

(答案→)C. could have expressed

D. must have expressed

解析：考查虚拟语气。根据did说明本句是对过去情况的虚拟，故使用情态代词+have done,排除AB。D想是对过去情况的推测，而不是虚拟。Could have done本可以做某事，实际上却未做。句意：David不后悔说他所做的，但是感觉他本可以用另外一种方法来做。故C正确。