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。
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