Alice didn't want her parents to know______ A how she had done B what she was doing

问题描述:

Alice didn't want her parents to know______ A how she had done B what she was doing
我知道答案是B,但是说不出A为什么不行,请大家从语法角度给我分析一下.

do是一个及物动词,后面要接宾语,而how是一个疑问副词,不能作动词的宾语,所以how she had done ,这句话存在了语法错误.
只能选择B.