英语语法loudspeakerswerefixedinthehallsothateveryoneshouldhaveanopportunitytohearthespeach.为什么主句是过去式就用shouldhave?和should有什么关系?

Question

英语 语法
loudspeakers were fixed in the hall so that everyone should have an opportunity to hear the speach.
为什么主句是过去式就用should have?和should 有什么关系?

Answer 1

虚拟语气的几个基本形式：
从句 主句
过去 had done should/would/might/could have done
现在 did/were should/would/might/could do
将来 did/were should/would/might/could do
were to do
should do
这句话就是将来时的基本型