Before you listen, you can read the questions and the choices.
以上句子摘自高中英语新教程-人教版-高中一年级必学1第12页。老师说这里的 before youlisten 可以换成 before listening，如此的改写有哪些规律吗？
老师说的没错：
Before you listen, you can read the questions and the choices.
=Before listening, you can read the questions and the choices.
听之前你可以先阅读问题和选项。
注意能如此改写的首要条件是从句主语与主句主语相同。又如：
Before making a decision , you need to weigh up the pros and cons of the situation. 在作出决定之前，你需要权衡形势的利弊。
Before getting divorced , you should think carefully about the effect it will have on the children. 离结婚以前，你应该慎重地考虑考虑这将会给孩子们带来哪种影响。
Before meeting with a client , you must try to erase any preconceptions you may have about them. 在和顾客会面之前，应该尽量消除任何有关他们的先入之见。
When singing this song , you stand in a circle, cross your arms over, and shake the hands of the people on each side of you. 唱这首歌时，你们站成圆圈，手臂交叉，与两旁的人拉手。
再以 when 举几个例子：
When preparing meals , you need to think about variety and taste as well as nutritional value. 做饭时，你既需要考虑饭菜的营养成分，又需要考虑饭菜的花样和味道。
When driving on the highway , you need to make sure no one is in your blind spot before changing lanes. 在公路上驾驶时，你需要先确保视线盲区里没人，然后再变换车道。
When asking who you are speaking to on the phone , you use the pronouns this in U.S. English and that in British English.打电话询问他们是哪个时，在美国英语中用this，在英国英语中用that。