改错题：we should keep in mind the necessity that every person must save the energy resources.we should keep in mind the necessity that every person must save the energy resources为什么要把must改成should?
问题描述：
改错题：we should keep in mind the necessity that every person must save the energy resources.
we should keep in mind the necessity that every person must save the energy resources
为什么要把must改成should?
答
it is +necessary +that clause(虚拟语气)是我们都知道的的语法结构，但是这里的necessity后的从句也要用虚拟语气，也就是should+do 的形式。所以must应改为should。
答
可从词义理解，从语法角度讲，与前面SHOULD的相对应。
答
must和should都有表示应该的意思,一般来说must是带有命令色彩的词,而should比must委婉点,这句话中,语法是没错的,但是不符合语言习惯,所以用should.
谢谢采纳!
答
should为情理上的应该
must为理智上的必须