369　in doing和on doing

① in doing意为“在做某事时”，in相当于 when 或 while。

In walking past the library，I met Professor Wang.我路过图书馆时，碰见了王教授。（=When I was walking…）

In reading a collection of poems in my study，I heard a bird twittering outside the window. 我在书房里读一本诗集时，听到窗外有一只鸟在叫。（=While I was reading…）

② on doing意为“一……就”，on相当于 as soon as，immediately。

On arriving there，we all set to enthusiastically. 我们一到那里马上就干劲十足地干了起来。（=As soon as we arrived there…）

On hearing “help”，he rushed out. 他一听到呼救声就冲了出去。

提示

on doing 也可表示“在……的时候”。

On turning the corner，she saw a skyscraper. 拐过街角，她看见了一幢摩天大楼。