1.主语从句
在主语从句中用以表示惊奇、惋惜、理应如此等意,其谓语用should +动词原形,should 在口语中可省略.主要用于以下三种结构：1)Itis necessary/important/natural / strange/essential /advisable/desirable/urgent …+that...如：It is necessary that he (should) get everything ready by tomorrow evening.到明天晚上前把一切准备好是必要的.It is important that you (should ) read English aloud every morning.你们每天早上朗读英语很重要.2) It is a pity (a shame,no wonder...)+that...如：It is a pity that she (should )be so careless.她这么粗心真是遗憾.It is no wonder that they (should) go there by air.难怪他们要坐飞机到那里去.3) It is suggested( decided,ordered,requested,desired,demanded,required,proposed,recommended) that ...如：It is requested that that factory (should) stop polluting the river.要求那家工厂停止对那条河的污染.It is decided that the sports meet (should) be put off till next week.已决定运动会推迟到下星期.
2.宾语从句
1) 在表示命令、建议、劝告、欲望、要求、主张这一类动词后的宾语从句中,从句应用
虚拟语气,其谓语用should+动词原形,should可省略,这类动词有suggest,insist,demand,request,desire,order,ask,advise,propose ,command,recommend,require等,如：The teacher insisted that we (should) use an English-English dictionary.老师坚持要我们使用英英词典.I suggest the invitation to the conference (should) be sent to Dr Baker.我建议给贝克博士发出出席的邀请.
表语从句
当表示间接的要求、建议、命令、决定、欲望、劝告、主张等名词作主语时,其表语从句用虚拟语气.这类名词有suggestion,proposal ,request,order,advice,idea,demand,recommendation等,其谓语用(should)＋动词原形.如：Our suggestion is that you (should) be the first to go.我们的建议是你应该先去.My idea is that he (should) do his homework first.我的想法是他先做作业.4.上述名词的
同位语从句也用虚拟语气,其谓语用(should)＋动词原形.如：Do you know the order that you (should ) keep watch 你知道你该去放哨的命令吗?We all agreed to his suggestion that we (should ) go to Beijing for sightseeing.我们都同意他要我们去北京浏览的建议.