英语中in 的短语什么时候可以省略

(1) 在 in this way, in that way, in the same way, in another way 等表达中的介词in 通常可以省略：　　Do it (in) this way。 这样做。　　Let me put it (in) another way。 让我用另一种方式解释。　　(2) 许多动名词前的介词in可以省略：　　Be careful (in) crossing the street。 过街道要小心。　　He lost no time (in) answering the question。 他马上就回答了那个问题。　　但若介词 in 出现在句首,则通常不宜省略：　　In crossing the street he was run over。 他在穿过马路时被汽车撞倒。　　在这类用法中要非凡注重一些常用句型： 　　be busy (in) doing sth 忙于做某事 　　be late (in) doing sth 做某事做晚了或做迟了　　spend money [time] (in) doing sth 花钱(时间)做某事　　waste money [time] (in) doing sth 浪费钱(时间)做某事　　have luck (in) doing sth 做某事时有运气(走运)　　have difficulty (in) doing sth 做某事有困难　　have trouble (in) doing sth做某事有困难　　have bother (in) doing sth 做某事费劲 　　have a problem (in) doing sth做某事有困难　　have a good time (in) doing sth 做某事很开心　　have a hard time (in) doing sth 做某事很辛劳　　find difficulty (in) doing sth 做某事发现有困难　　There is no difficulty (in) doing sth 做某事没有困难　　There is no use (in) doing sth 做某事没有用　　There is no point (in) doing sth 做某事没有意义