She likes to play the piano while her brother ________to music.
A listen
B likes listening
C is listening
D listen

She likes to play the piano while her brother ____A____to music.
A listen
B likes listening
C is listening
D listen

为什么A,D选项一样呢?还是有一个选项是likes to listen?
这里的while作连词解释为“而, 然而”，通常表示前后的一个对比或相反的情况。如：I drink black coffee while he prefers it with cream.前后句形式类似的时候要保持一致的用法，所以前面是likes to do，后面也要likes to do，不能用likes doing，另外如果解释为“当”而选C是不通的，不是当她兄弟听音乐的时候她才喜欢玩钢琴。而是：她喜欢钢琴，而她兄弟却喜欢听音乐。根据你的选项只有（likes to）listen最适合。