be +adj+to do It is + adj + that从句，什么时候不用虚拟

It is + adj + that从句，什么时候不用虚拟  

It is + adj + that从句，什么时候不用虚拟

并不是所有It is + adj + that从句的形式都用虚拟语气的.你这个句子只是一种陈述,而不是建议、愿望、请求、命令……等.
详细介绍如下：
在形如“It is (was)+形容词（或过去分词）+that……”结构中,使用某些表示愿望、建议、请求、命令、可能、适当、较好、迫切、紧近、重要等形容词后的主语从句的谓语也用虚拟语气.其表达形式为should ＋动词原形或省略should直接用动词原形（美国英语中省去should）
常用的形容词：* natural (自然的),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 (很可能的),possible (可能的)* desirable (极好的)advisable（合理的）,pulsory（必须的）,crucial（紧急的）,desirable（理想的）,essential（必要的）,imperative（迫切的）,incredible（惊人的）,necessary（必要的）,possible（可能的）,strange（奇怪的）,urgent（紧迫的）.
常用的过去分词(Past Participle):* required (需要的),demanded (要求),requested (被请求的),desired (要求)* suggested (建议),remended (推荐)* orderd (命令)
1.It is necessary that we (should 可省略,下同）have a walk now.(necessary,should + have) (表示有需要去散步)
2.It was necessary that we (should) make everything ready ahead of time.(necessary,should + make) (表示有必要事先做好准备)
3.It is required that nobody (should) smoke here.(required,should + smoke) (表示要求不要在此抽烟)
4.It is important that every pupil (should) be able to understand therule of school.(important,should + be) (表示重要的是学生都能了解校规)
5.It’s important that we (should) take good care of the patient.(important,should + take) (表示重要的是照顾好病人)
6.It is natural that she should do so.(形容词natural,should+动词原形do)
7.It is essential that these application forms be sent back as early as possible．这些申请表应尽早地寄回,这是很重要的.
8.It is vital that enough money be collected to fund the project．重要的是募集足够的钱,为这个项目提供资金.
9.It is desired that we（should）get everything ready this evening．希望我们今晚一切都准备就绪.
注：在上述所列形容词后面用that引出的宾语从句中,谓语动词也要用虚拟语气.
10.I don’t think it advisable that Tom be assigned to the job since he has no experience．汤姆缺乏经验,指派他做这项工作我认为是不恰当的.

您好
不一定.如It is true that the earth travels round the sun.地球绕太阳转,这是事实.
It's kind of you that you have helped you so much these years.这些年你帮了我这么多,你这人真好!
It was right that the temple was rescued.拯救这座寺庙是做得对的.
这种结构中的it是形式主语,真正的主语是由连词that引导的主语从句.
这种结构可以换成It is + adj. +for+n.+不定式的复合结构.如：
It is quite likely that the meeting will be put off till tomorrow.会议很有可能推迟到明天开.
=It is quite likely for the meeting to be put off till tomorrow.
It is important that he should know about this. 他必须知道此事。
It’s vital that we be present. 我们出席是至关重要的。
It was intended that you be the candidate. 大家的意图是让你当候选人。
It is important that this mission not fail. 这项使命不失败至关重要。
It is essential that a meeting be convened this week. 本周开一次会非常重要。
It is appropriate that this tax be abolished. 废除这个税是恰当的。
It’s unfair that so many people should lose their jobs. 竟有这么多人失业这是不公平的。
It’s amazing that she should have said nothing about it. 她竟未谈及此事令人惊讶。
It’s unthinkable that they should deny my request. 他们竟然拒绝我的请求，这是不可思议的。

for fear that后面接从句什么时候不虚拟

for fear that后面从句用should+动词原形来虚拟
should没有意思的，可以省略
He put his coat over the soldier for fear that he （should） catch cold
不过现在的趋势是像这种句子一般不用虚拟了，直接用陈述语气
I dare not go there for fear that he will see me
正统的话就用虚拟，从实用主义出发，就不用

in case 接从句时什么时候用虚拟语气？什么时候不需要？

in case 接的从句是事实就不用虚拟，不是事实就用虚拟。跟as if 类似吧。。。

if引导的从句什么时候用虚拟语气

if引导的条件状语从句的分类及虚拟条件句的判断
1、可以把条件句分为两类：
1).真实条件句（Sentences of Real Condition）：凡是假设的情况发生性可能很大，就是真实条件句。例如：
⑴、If I have time , I will help you with this work.如果我有时间会帮助你做此工作的。
⑵、As long as I say anything wrong, you must point it out.只要我说了什么错话，你一定要指出来。
⑶、If time permits, we'll go fishing together.(如果有时间的话，我们就一起去钓鱼。）
2).虚拟条件句（Sentences of Unreal Condition）：当假设是不大可能实现时，就是虚拟条件句。例如：
⑴、If I were you , I would have attended the meeting. 如果我是你的话，就去参加会议了。
⑵、If he had e here yesterday, he would have seen his old friend.假如他昨天来这儿的话，就会看见他的老朋友。
⑴、If it had rained yesterday, we would have stayed at home.（如果昨天下雨的话，我们就会留在家里。）
2、.if条件状语从句中虚拟语气的判断
判断是真实条件句还是非真实条件句。只有在非真实条件句中才使用虚拟语气。通过句子意思，看假设的条件是否能够实现，能够实现是真实条件句，不能使用虚拟语气；假设的条件不能实现则是非真实条件句，要用虚拟语气。
判断这个假设是与哪个事实相反。通常有三种情况：①与过去事实相反。②与现在事实相反。③与将来事实可能相反。
3、“后退一步法”
后退一步法是指在准确地判断了该句与哪一事实相反后，按虚拟语气的后退一步法处理从句谓语动词的时态。即：在非真实条件状语从句中，谓语动词按正常情况“后退一步”。也就是：
①与过去事实相反，在从句中用过去完成时形式表示。
②与现在事实相反，在从句中用过去一般时形式表示。
③与将来事实可能相反，在从句中用过去将来时形式表示。
主句中则用情态动词would, should, could 等加一个与从句一致的动词形式。例：
⑴、If I had e her yesterday, I would have seen him.
⑵、If I were a teacher, I would be strict with my students.
⑶、If it should snow tomorrow, they couldn't go out.
4、注意事项
①if条件句中如有were, should, had，可以省去if，并使用倒装语序。
②在现代英语中if条件状与从句中的谓语动词如果是be其过去形式一般用were。