一、It’s important…类 这一类型主要包括It is (was) important (necessary, desirable, imperative, advisable)that. . .句型。如： It is impossible that he should go home. 他不可能会回家去。http://yingyu.chazidian.com It is necessary that I should return it right now. 我有必要马上把它还回去。 It is important that we should speah politely. 我们说话要有礼貌，这是很重要的。 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 imperative that we should practise critidsm and self-criticism. 应当进行批评与自我批评。
二、It’s a pity…类 It is a pity that she should fare so badly. 她竟吃得这么差，真可怜。 It’s a pity that he should be so obstinate. 真遗憾他竟这样倔犟。 It was a pity that you couldn’t come. 你不能来，真是太遗憾了。 It is a pity that she failed the driving examination. 她没通过驾驶考试真是遗憾。 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。
三、It’s desired…类 这种主语从句还常用在It is (was) desired (suggested, settled, proposed, requested, decided, etc. ) that...句型。如： 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。 【特别说明】 (1) 在现代英语中，有时也可不用虚拟语气而用陈述语气，但初学者宜慎用。 (2) 在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。 若不用虚拟语气也可以，则不带感情 色彩，比较： 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。