David apologized for to inform me of the change in the plan.A. his being not able

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A. his being not able　　　　　　　　
B. him not to be able
(答案→)C. his not being able　　　　　　　　
D. him to he not able
解析：介词for后应用动词的-ing形式，排除B、D；所有非谓语动词的否定词not都应加在非谓语动词之前，即not to do ,not doing, not having done, not done,故选C。