on finishing the article,I will return the book to you as soon as possible.这句话中on怎么解释?

问题描述:

on finishing the article,I will return the book to you as soon as possible.
这句话中on怎么解释?

一读完这篇文章,我将尽快把这本书还给你。on在这里表示时间。

其实没有on这个句子也对
有on,表示强调,就是说"一"完成这个文章..