When doing与while doing有何本质上的区别?When reading可否放在句首?

When doing与while doing有何本质上的区别?When reading可否放在句首? ***WHEN与WHILE用法区别? while与when怎么分 when和while后面可以直接加动名词的短语吗,比如when/while doing sth when和 while前后加DO或DOING的形式 while sb was/were doing与when sb was/were doing有什么区别呢?什么时候用前者,什么时候用后者 when doing 和 while doing 的区别when doing 和 while doing 有什么区别?最好有相关造句说明.还得有中文解释啊 what were you doing when he arrived为什么是 when 不是while when 和while 后面跟什么时态 While的用法及while与when的区别. when while as造一句!是不是while在不表对比时!就可以与when互换!如：The telephone rang while I was doing my homework.We must strike while the iron is hot.(这句可以换when吗?）还有用as表一边……一边……时造个句! when与while有什么区别? when与while的区别及用法? when与while的区别 有例子 while 与when 用法区别fff what were you doing __your father__back?A.while ;came B.when ;came C.while ;was coming D.when ;was coming 各举一个be+doing+while+be+doing和be+doing+when+did的例句,be最好为过去时 英语问题while与when的区别,用法的区别,什么时候when在前面,什么时候while在前面, a.What were you doing when it rained.b.What were you doing while it was raining.