as 与when,while在这道题中的区别?My father visited my school last May,___I was taking an exam.A.while B.when C.as D.whenever为什么?为什么不能是A或C?

as 与when,while在这道题中的区别?My father visited my school last May,___I was taking an exam.A.while B.when C.as D.whenever为什么?为什么不能是A或C? when,while,as在状语从句中的用法?抄笔记漏了,要补充 while,as,when 区别? when while as 区别 As while when 在表示当什么时候时有没有区别 请问,when while在过去进行时句子中的用法与区别? WHEN 与while在过去进行时中的区别求例句,越多越好. as when while 的区别 When While As 的用法 when ,while,as的区别 while,as soon as,when的区别 as soon as ,when,while 什么区别 as与while区别 when,while,as soon as,before,after的区别从句与主句各是什么时态 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! 谁知道When和While在句中的用法区别 when和while在句子中的时态一样吗? as/since/until/when/while的区别