Tom pretended it but in fact，he knew it very well.
A. not listen to
B. not to hear about
C. not to have heard about
D. not to be listening to
网友回答
A. not listen to
B. not to hear about
(答案→)C. not to have heard about
D. not to be listening to
解析：此处用不定式的完成式表示该动作发生在前。