before doing sth before making a decision,think it over.为什么用making?

before doing sth还是do sth before doing sth 和 before you do sth,为什么? help,open的过去分词是什么?是before sb do sth.还是before sb doing sth... before sb doing还是do sth如题``` before doing sth before making a decision,think it over.为什么用making? before什么时候加doing sth./sb.do sth.什么时候before后加一般过去时的句子或过去完成时的句子 求 before doing sth的用法?He was sad before doing sth.就是before doing sth 前可以不可以用过去时态.不行的话,那应该如何表示 去电影院前,我去了图书馆.是过去时态. 翻译 prefer doing sth to doing sth perfer doing sth to doing sth look at doing sth have fun doing sth dislike doing sth help sb doing sth 造句:consider doing sth enjoy doing sth? sb doing sth是什么意思? turn to doing sth. have fun doing sth.