while doing sth 省略什么 为什么

while doing sth 省略什么 为什么 I'm always listening to music____doing my homework为什么空格处填while,不填as?后半句为什么可以省略主语?做题时我都是碰到I'm doing sth while i'm doing sth没人知道么````` T T I'm always listening to music____doing my homework为什么空格处填while,不填as?后半句为什么可以省略主语?做题时我都是碰到I'm doing sth while i'm doing sth............ prefer doing sth to sth动词一样是否可以省略动词prefer doing sth to doing sth如果两个doing一样是否可以省略第二个doing prevent sb. (from) doing sth （from可省略） 等于keep sb. (from) doing sth（from可省略） 还等于什么prevent sb. (from) doing sth （from可省略）等于keep sb. (from) doing sth（from可省略） 还等于什么?我只记得 Don't leave the water (running )while you brush you teeth. 为什么是running?leave sth doing sth?什么意思? keep sb.from doing sth.和stop sb.from doing sth.中哪个from可以省略 while I was doing可省略I was吗 stop sb from doing sth 中from可以省略吗 have trouble 【in】doing sth?in可以省略? succeed in doing sth 中 in可以省略吗? Help sb in doing sth中的in可以省略吗?. succeed in doing sth 的in可以省略吗?阿 assist sb in doing sth中in可否省略? succeed in doing sth.这里的in能不能省略? fail in doing sth中的in能不能省略 prefer doing to doing sth什么意思 mind doing sth什么意思?