All that must be done ____(do).答案是have been done,为什么是这个答案?这句

来源：学生作业帮编辑：作业帮分类：英语作业时间：2024/10/06 09:08:35

All that must be done ____(do).答案是have been done,为什么是这个答案?这句话是现在完成时吗?
我看了其他人的回答是这样的：打括号的是定语从句,修饰主语all.
翻译：所有必须做的事情都已经被做好了.
此处All可以视为单数,也可以视为复数.为什么我们英语组长给出的是have been done?究竟哪个对?

all 用做主语时,谓语动词用单数还是复数取决于它的意义.
当all 作：“大家” 讲时,当然用复数.如：All are excited to see the movie star.
当all of + 复数名词作主语时,谓语动词也用复数.如：All of the trees have been cut down.
当all作“一切”讲时,谓语动词用单数.如：All has been changed.
All I want is just a cup of tea.
所以例句中的空应该是has been done 整句话应该是：
All that must be done has been done.

All that must be done ____(do).答案是have been done,为什么是这个答案?这句 must have been done/must be done All that must be done----(do) all that can be done has been done 为什么要用has,不用have all that can be done been done. must have been done must have done MUST have been done can be done was done could be done must have been done will all that can be done has been done Has all that can be done been done? all that can be done has been done. all the things should be done have been done already