When (she was) very young,she began to learn to play the piano.她很小時,就開始學習彈鋼琴.
While (I was) at college,I began to know him,a strange but able student.我在上大學時就開始認識他,一個奇怪但有能力的學生.
When arriving,send me a telegram.(When you arrive,send me a telegram.) 到達之后,來個電報.
Before leaving,turn off all the lights.(Before you leave,turn off all the lights.) 走之前,請關閉所有的燈.
Don’t come in until (you are) asked to.不叫你請你不要進來.
Whenever (it is )possible,you should come and help.不管什么時候只要有可能就來幫忙.
You should let us know the result as soon as(it is) possible.你應盡快讓我們知道結果.
注：as在引導時間狀語從句時,沒有這種省略現象.我們不可說As walking,she found a nice shining thing on the ground.