问题补充：
David apologized for to inform me of the change in the plan.
A. his being not able
B. him not to be able
C. his not being able
D. him to be not able
答案：
A. his being not able
B. him not to be able
(答案→)C. his not being able
D. him to be not able
解析：句意：大卫向我道歉因为没有通知我计划的变化。这里apologize for因为……而道歉，因为for介词后用动词，这里是动名词的复合结构的否定形式，not应该在动名词的前面，故选C。
