listen/listen for/listen in的用法（比如后面能接什么）

listen -- 除了for/in，还可以接to
listen for -- 留意地倾听，例
I listened for his footsteps. 我倾听以便觉察他的脚步声。

listen in -- 外来者加入对话型的听，例：
I'm not taking the class, but can I listen in? 我没修这门课，但是可以来旁听吗？

我把LONGMAN的解释给楼主看看， 参考一下吧

listen for: to pay attention so that you are sure you will hear a sound

listen in: A. to listen to a broastcast on the radio; B. to listen to someone's conversation without them knowing it

listen out: to listen carefully, especially for an unexpected sound

listen up: used to get people's attention so they can hear what you are going to say