32.(1)______ what the schoolmaster said, the girl’s face turned red.

题目

32.(1)______ what the schoolmaster said, the girl’s face turned red.
(2)_______ what the schoolmaster said, she was encouraged.
A. After she heard B. After hearing C. To hear D. To be heard
第一小题答案是A 但B为什么不可以,我觉得AB是一样的,请指教,谢谢.

答案

B答案里是一个分词短语,用了这个,后面主句中的主语就可以不是女孩本身,可以用女孩的脸做主语了
然而A选项中用“在她听到...之后”就暗示着后面主句的主语应该用女孩,而不能随意更换为别的主语了
希望你能明白