唉.你们这些光看语法书的啊,今天回答了N个问题都是
确实都可以,而且蛮常用,也不偏
1、by which 后面接定语从句这个没问吧
2、by which time的用法举个例子
eg:In fact, according toDrEdmunds, the real peak occurred in October, by which time fewer people were seeking medical help.
事实上,据埃德蒙博士研究,真正的激增发生在10月,这段时间求医问药的人相对较少.
这里which time 更像一个“代词”,代前面的 october. 把by which time 替换成when 也行.
3、when 一可以接时间状语从句罗