when和while的区别,怎样用
问题描述：
when和while的区别,怎样用
答
1. 当从句中的谓语动词是持续性的动作时,我们可以用while, when或as. While / When / As I was walking down the street, I noticed a police car in front of the bank.我顺着马路往前走时,发现银行门前停着一辆警...