主语从句涉及到虚拟语气的词汇不多，但是考试较为常见，要逐个记忆用法。
总体句型模式：It is n(adj,pp) that-clause
注意that所引导的主语从句中有时用虚拟语气即谓语动词用"should 原形"或省略should,表虚似语气；其中由that引导的主语从句通常用“should 动词原形”这样的虚拟语气，其中的should在美国英语中通常省略。如：
这类的名词有：advice,decision,desire,demand,idea,motion,order,pity,preferce,proposal,recommendation,requirement,resoluction,shame,suggestion,surprise,wish,wonder
这类形容词有:natural自然地,appropriate适当的,advisable合适的,preferable更可取的,better更好的,necessary必须的,important重要的,imperative急需的,urgent急迫的,essential本质的,vital必不可少的,probable有可能的,possible可能的,desirable理想的, advsible合理的,imperative迫切的,incredible惊人的,necessary必要的,possible可能的,strange奇怪的,urgent紧迫的;compulsory必须的，crucial紧急的
这类过去分词有：required需要的,demanded要求,requested被要求的,desired要求,suggested建议,recommended推荐,ordered命令; settled决定， urged主张，decided决定, proposed提出，advised建议
例如:
It is necessary that the problem should besettled at once.
这个问题必须马上解决.
It's strange that he should have gone awaywithout telling us.
他竟然没向我们说一声就走了,真是奇怪.
It’s important that we (should) reply to her letter. 回复她的信是重要的。
It is important that we should speah politely. 我们说话要有礼貌，这是很重要的。
It is necessary that I should return it this morning. 今天早上我就有必要还回去。
It is not necessary that everyone be a scientist. 没有必要使每一个人都成为科学家。
It is impossible that he should go home. 他不可能会回家去。
It is essential that the meeting start at eight. 会议务必在8点钟开始
It is essential that we should tell her the news. 我们有必要告诉她这个消息。
It is desirable that everything should be ready by five o’clock. 最好一切在5点前准备就绪。
It is desirable that there should be a cold season once a year. 每年有一个寒冷的季节，是很令人盼望的。
It is advisable that everyone should have a map. 最好每一个人都有一张地图。
It is advisable that he should see a dentist regularly. 他定期去看牙科医生是明智的。
I was glad that she should go. 我很高兴她能去。
It is imperative that we should practise critidsm and self-criticism. 应当进行批评与自我批评。
It is a pity that she should fare so badly. 遗憾，她竟过得如此糟糕。
It was a pity that you couldn’t come. 你不能来，真是太遗憾了。
It is his desire that a medical man should stay here. 他希望有一个医务人员留在这里。
It's right that you should think that way. 你这样想是对的。
It has been suggested that the meeting（should）be put off．有人建议推迟会议。
It is requested that a vote be taken. 建议付诸表决。
It is settled that you leave us, then? 那么你肯定要离开我们罗?
It was proposed that this matter be considered at the next meeting. 有人提议这事下次会议再讨论。
It is desired that this rule should be brought to the attention of the staff. 希望这条规则引起全体职员的注意。
I’m surprised that he should have failed. 他竟然失败了，这使我很吃惊。
It is amazing (strange, surprising, astonishing, a pity, a shame)以及 I am surprised (sorry) 和I regret等结构后的that 从句中有时也用should，表示说话人的惊异、懊悔、失望等情感，常含有“竟然”之意：
It’s strange that he should be so rude. 他竟如此无礼，真是奇怪。
I’m surprised that he should have failed. 他竟然失败了，这使我很吃惊。
注意：这种句型中的主语从句在语法上也可用陈述语气，如：
It was important that he made an explicit statement on this score last week. 他上个星期对于这一方面做了明确的说明，这是很重要的。
陈述句仅仅只是实事求是地说明情况，没有感情色彩。虚拟语气却带有明显的感情色彩。
It’s a pity that he failed the exam. 他考试没及格，真是遗憾。
It’s a pity that he should have failed the exam. 他考试竟没及格，真是遗憾。
