when, while , as的用法when当(在....时: ( = at the tine that), 可表示瞬间、时间段,与主从句所述动作、事情可同时,也可有先后:It was snowing when we got to the airport. 我们到达机场时,天正下着雪。(同时发生) He went horne when he had finished his homework.做完作业后他回家去了。(先后发生) while正当(正在...时;(指同时=①for as long as②during the time that),用于同时进行的两延续性动词相伴随而发生,常对同类的两动作进行对比:Please write while I read. ( = during the time that )我念的时候,请写下来。 I am safe while l am here.(=for as long as)只要我在这儿,我就安全。 Some students were reading while others were. writing.有些学生在读,而有些学生在写。( 进行对比) as当....时;强调at the same time,①不指先后,而指并相发生,尤指短动作或事件同时发生: As I looked, some one came near. 正当我看的时候,有个人走上前来。 ②as还可说明两种正在发展或变化的情况:As I get older I get more optimistic. 我越活越乐观。 as,when或while可引导时间较长的“背景”情况: As ( When,或While) I was walking down the street, I noticed apolice car in front of Number 37. 我顺着马路往前走,发现37号门前停着- .辆警车。 |
|