“常用在It is (was)+形容词 / 过去分词+that引导的主语从句”的句型中的主语从句要用虚拟语气。主语从句的谓语用should+动词原形(或should+have+过去分词)或只用动词原形(尤其是美国英语)。should在此是助动词，本身并无实义，这种主语从句中的should有时有感情色彩。
It's important that we（should）work out a plan. （带有“要求”的含义）
It's better that he go at once. （带有“建议”的意思）
☆ 用于本句型的形容词并不多，常见形容词有：necessary，important，best, right, impossible，preferable，desirable, imperative, advisable，essential，reserved，urgent， 等。
It is necessary that he（should）be sent there at once．
It's strange that he should say so.
I was glad that he should go.
It is important that we should speak politely.
It is a pity that she should fare so badly.
It's right that you should think that way.
☆用于本句型中的过去分词就是表示提议要求、命令等动词的过去分词，如suggested，settled, required，requested，demanded，urged，decided, proposed，ordered，desired，advised等。
It is requested that Professor Liu（should）give us a lecture．
It is desired that we（should）get everything ready by tonight．
I’m ashamed you should have done such a thing.
It has been suggested that the meeting（should）be put off．有人建议推迟会议。
It is settled that you leave us, then?
注意：这种句型中的主语从句也可用陈述语气，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。
1). 宾语从句在表示提议、要求、命令、意志等动词后，其谓语用should+动词原形或只用动词原形的虚拟语气，作为suggest，request，demand，urge，propose，prefer，advise，insist，require，order，command，maintain，ask，object, arrange, desire等动词的宾语。
The doctor suggested that he not go there．医生建议他不要去那里。
He suggested that we should leave early. 他建议我们早点动身。
The judge ordered that the prisoner should be remanded. 法官命令被告还押。
I wish it were true．我但愿这是真的。
I wish you would stay a little longer.我希望你再待一会儿。
☆ 表示无能为力的过去愿望（与过去事实相反），可用“had +过去分词”或“could（would，might）+have+过去分词”
I wish you had called yesterday．我希望你昨天来过电话。
We wish you had come to our New Year’s party.我们真希望你来参加了我们的新年联欢会。
3). would rather, would sooner等表示愿望，其宾语从句常用虚拟过去式。
☆ 用过去完成式(had + 过去分词)表示过去事实相反的含义
I would rather you came tomorrow.我宁愿你明天来。
I’d sooner she left the heavy end of the work to some one else.我宁愿她把重活留给别人。
4). 有些动词，如think, expect, believe,其否定式的宾语从句亦可用should+动词原形。如：
I never thought he should refuse.我万没有想到他会拒绝。
She did not expect that you should come.她没有预料你会来。
My suggestion is that we (should) send a few soldiers to help them.
My advice is that you (should) treat her well. 我的忠告是你应该善待她。
He makes the demand that she (should) leave the place at once.
My suggestion is that we should tell him.我的建议是我们应该告诉他。
Our only request is that this should be settled as soon as possible.
如：There was a suggestion that Brown should be dropped from the team.有一项建议是布朗应该离队。
常用在It is time (that)…句型中，定语从句常用虚拟过去式
It is time the children went to bed. 孩子们早该上床睡觉了。（表示催促）
It's high time that he began to think how to deal with money.
It is time we left.我们该走了。
It is time we went to bed.我们该去睡觉了。
Long live the Communist Party of China！中国共产党万岁！
God bless you! 上帝保佑你。
God damn it! 该死的！
The devil take you! 见鬼去吧！
So be it then. 就那样吧。
It is important that he should know about this.他必须知道此事。
It was important that he should know about this.他必须知道此事。
I suggest that we should go tomorrow.我建议我们明天走。
I suggested that we should go the next day.我建议我们第二天走。
She said, “If I were a boy I would join the army.”她说，“我如是男孩，就参军。”
She said that if she were a boy, she would join the army.她说她如是男孩就参军。
“If I knew how it worked, I could tell you what to do,” he said.
He said that if he had known how it worked he could have told me what to do.
“If I knew the answer to all your questions I'd be a genius,” he said.
He said that if he knew the answer to all my questions, he’d be a genius.
如：I would think he was wrong.我看他是错了。(须用was,试比较：I think he is wrong)
It would seem that she was right. 她似乎是对的。(须用was,试比较：It seems that she is right)