I her but I never could.A. ought to helpB. must helpC. ought to have helped D. must have

问题补充：

I her, but I never could.

A. ought to help

B. must help

C. ought to have helped

D. must have helped

答案：

A. ought to help

B. must help

(答案→)C. ought to have helped

D. must have helped

解析：本题考查ought的用法。ought to + have+done表示过去应该做某事却没做。