同学你好，该知识点来自沪江网校《2021考研VIP协议班 政治+英语一【全额奖学金班】》的课程，想要更系统的学习，欢迎进入课程学习。不仅可以和更多的同学一起学习，而且还有老师、助教随时的学习指导和知识点解答哦。

主从句表达的事件发生时间bai一du致的话，时态必须一致。zhi但主从句事件时间不同，时态就可以不dao同。例如He was so poor then that he now wants to express his thanks to those who helped him.