Question

when,while as区别

Answer 1

回答如下：
1. 若某事正在进行时又发生了某事，我们可以用when，while和as。when, while和as引导的时间状语从句的谓语动词必须是延续性动词，主句谓语动词必须是短暂性动词。例如：
When / While / As I was walking down the street, I noticed a girl hit by a truck.
不过as引导的时间状语从句还可以用一般时。例如：
As I sat at the desk writing, I didn't notice her come in.
2. 若时间状语从句的谓语动词是非延续性动词时，不能用as和 while，可以用when。例如：
When we arrived at the school, it was nine o'clock in the evening.
3. 若主句和从句的两个动作是同时进行的长动作，通常用while，从句可用一般时或进行时。例如：
While the boy was watching TV / watched TV, his mother was doing the cooking / did the cooking.
4. 若表示两种正在发展、变化的情况，可以用as。例如：
As I get older, I get more optimistic.
As it grew dark, we were more and more worried about her safety.
5. 若是两个短动作，通常用as或just as, 也可以用when 或just when。例如：
Just as / when I opened the door, a strange man appeared in front of me.

Answer 2

1.作“当…时”区别不大，属于比较，主观性的遣词造句范畴，
2.考试一般是在区别上考，while当转折比较，as当原因（as用法相当多了）这时它们就各不相同了。