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

问题补充：

I her, but I never could.

A. ought to help

B. must help

C. must have helped

D. ought to have helped

答案：

A. ought to help

B. must help

C. must have helped

(答案→)D. ought to have helped

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