It be /seem +(表示愿望、建议、命令、要求、意志、惊讶、不满、遗憾等意义的)形容词/过去分词/名词 + that + 主语+(should)+动词原形.
在本结构中it是形式主语，真正的主语是后面的that从句， 从句中谓语动词的形式为should do, should 可以省略。
4.1. It is + adj. + that + … (should) do …
advisable明智的 amazing令人吃惊的 disappointing令人失望的
embarrassing令人尴尬的 essential重要的 important重要的
incredible令人难以置信的 natural自然的 necessary 必需的,不可缺少的
strange奇怪的 surprising令人惊讶的 vital 至关重要的
urgent紧急的 astonishing 令人惊讶的 imperative 势在必行的
1). It is natural that he object to a plan like that.
2). It is necessary that we tell him the truth at once.
3). It is not necessary that everyone be a scientist.
4). It is essential that every child be given the same educational opportunities.
5). It is urgent that a doctor should be sent for immediately.
6). It is advisable that everyone have a map.
7). It is vital that the headmaster receive this letter this evening.
8). It is important that you should thank those who supported you through the disappointments.
9). It is really strange that the girl be married so early.(真奇怪，那小姑娘竟然这么早就出嫁了!)
10). It is amazing that he should have learnt so much in such a short time.
11). It is strange that he have left without saying good-bye.
12). It is surprising that he should be so foolish as to believe her lie
13). It was astonishing that she have kept the secret from him all through their lifetime.
14). It seems incredible that he have finished the work so soon.(他竟然这么快就完成了工作，这似乎令人难以置信。)
a. 在It is amazing/surprising/astonishing/strange/incrediable/a pity/a shame that ... 结构中，that虚拟从句表示说话人的惊讶、懊悔、失望等强烈的情感，含有“竟然, 居然”的意思，表明所发生的事情非常出人意料。如上面例句9-14。再如：
15). It’s a pity that he should miss the lecture.(真遗憾，他竟然错过了这次演讲。)
16). It’s a pity that he should turn down my offer.(真遗憾，他竟然拒绝了我的提议。)
17). It is a shame that she should behave like that.(她竟然表现的那么差劲，真丢人。)
b. 本结构还可形变为It is + of + 上述形容词相对应的名词形式+ that … (should) do…。如：
18). It is of utmost importance that you be here on time.
4.2. It is + 过去分词 + that … (should) do …
suggested ordered desired proposed decided
recommended requested required demanded
1). It is suggested that more trees should be planted to prevent sandatorms.
2). It is required that the students wear school uniforms at school.
3). It is decided that no smoking be allowed in the library.
4). It is demanded that one of the students should stay to look after the things.
5). It is proposed that this matter be considered at the next meeting.
6). It is recommended that the work shouldn’t be started until all the preparations have been made.