（1） 在主语从句中用来表示惊奇、惋惜、理应如此等,其谓语形式是"should(可省) ＋动词原形",常用于以下三种句型中.
句型一：It is necessary (important,natural,strange,etc) that…
句型二：It is a pity (a shame,no wonder,etc) that…
句型三：It is suggested (requested,proposed,desired,etc) that…
如：It is strange that he (should) have done that.
It is a pity that he (should) be so careless.
It is requested that we (should) be so careless.
（2） 在宾语从句中用于 suggest,propose,move,insist,desire,demand,request,order,command 等动词后的宾语从句中,表间接的命令和建议.其谓语形式是"(should) + 动词原形".如：
I suggest that we (should) go swimming.
（3） 在表语从句中,表示间接的命令,要求、请求、建议、决定等,主句中的主语通常是 suggestion,proposal,request,orders,idea 等.从句谓语形式是"(should)＋动词原形".如：
His suggestion is that we (should) leave at once.
（4） 在同位语从句中,谓语形式是"(should)＋动词原形".如：
We received order that the work be done at once.
（5） 在 It is time that …句型中,其谓语动词形式是"动词的过去式"或
"should ＋动词原形",should 不可省.如：It's time (that) we went ( should go) to school
