it引导的强调句结构：It is/was+被强调部分+that/who+句子其它部分。
eg:My father did the experiment in the lab yesterday evening.
强调主语：It was my father who did the experiment in the lab yesterday evening.
强调宾语：It was the experiment my father did in the lab yesterday evening.
强调时间：It was yesterday evening that my father did the experiment in the lab.(注意不用when)
强调地点：It was in the lab that my father did the experiment yesterday evening.
宾语从句
名词从句用作宾语的从句叫宾语从句。引导宾语从句的关联词与引导主语从句表语从句的关联词大致一样，在句中可以作谓语动词或介词及非谓语动词的宾语。
1. 由连接词that引导的宾语从句。
由连接词that引导宾语从句时，that在句中不担任任何成分，在口语或非正式的文体中常被省去，但如果从句是并列句时,第二个分句前的that不可省。
He has told me that he will go to Shanghai tomorrow. 他已经告诉我他明天要去上海。
We must never think (that) we are good in everything while others are good in nothing. 我们决不能认为自己什么都好，别人什么都不好。
注意：在demand、order梦见打雷下雨、suggest、decide、insist, desire, request, command, doubt等表示要求、命令、建议、决定等意义的动词后，宾语从句常用“（should）+ 动词原形”。
I insist that she (should) do her work alone. 我坚持要她自己工作。
The commander ordered that troops (should) set off at once. 司令员命令部队马上出发。
2. 用who，whom, which, whose, what, when, where, why, how, whoever, whatever, whichever等关联词引导的宾语从句相当于特殊疑问句，应注意句子语序要用陈述语序。
I want to know what he has told you. 我想知道他告诉了你什么。
She always thinks of how she can work well. 她总是在想怎样能把工作做好。
蒜蓉金针菇的做法
She will give whoever needs help a warm support. 凡需要帮助的人，她都会给予热情的支持。
3.可运用it做形式宾语。
①.动词make, find ,think,feel,consider,believe等后面有宾语补足语的时候，则需要用it做形式宾语，而将that宾语从句后置，结构：S.+vt+it+adj./n.+oc(宾语补足语)。
I think it necessary that we take plenty of hot water every day.我认为每天多喝开水是有必要的。
I feel it a pity that I haven't been to the get-together.我没去聚餐，感觉非常遗憾。
②.有些动词带宾语从句时需要在宾语与从句前加it，这类动词主要是：hate,take,owe,have,see to
I hate it when they with their mouths full of food.我讨厌他们满嘴食物时说话。
We take it that you will agree with us.我们认为你会同意我们的。
He will have it that our plan is really pratical.他认为我们的计划确实可行。
4.用whether或if引导的宾语从句，其主语和谓语的顺序也不能颠倒，仍保持陈述句语序。此外，whether与if 在作“是否”的意思讲时在下列情况下一般只能用whether，不用if：
①whether引导主语从句在句首时；
Whether there is life on the moon is an interesting question. 月球上有没有生命是个有趣的问题。
Whether he can come to the party on time depends on the traffic.他能否准时参加派对得看交通情况。
②宾语从句放在句首表示强调时，只能用whether；
Whether this is true or not, I really don't know.这是否真实，我也不知道。
③引导表语从句，只能用whether；
The question is whether we can get in touch with her.问题是我们是否能联系上她。
④引导介词宾语时,只能用whether；
His father is worried about whether he lose his work.他的父亲担心他是否会失去工作。
I'm thinking about whether I should quit my present job.我正在考虑我是否应该辞去现 在的工作。
Everything depends on whether we have enough money.一切要看我们是否有足够的钱。
⑤if与whether都可以与or not连用，但后面仅跟着淘宝评价or not时只能用whether；
We didn't know whether or not she was ready.（此时只能用whether）
I wonder whether/if the news is true or not.（此时则二者都可以用）
⑥后接动词不定式时，用whether；
Can you tell me whether to go or to stay? 行政经理你能否告诉我是去还是留？
I can't decide whether to stay.我不能决定是否留下。
⑦用if会引起歧义时，只用whether明晓溪的所有小说；
Could you tell me if you know the answer ?
这句话有两种意思：“你能告诉我是否知道答案吗？”或“如果你知道答案，请告诉我，好吗？”。如用whether可避免歧义.
⑧whether可引导同位语从句，if不能引导同位语从句。
The question whether we should call in a specialist was answered by the family doctor.我们是否请专家由家庭医生来定。
5. 注意宾语从句中的时态呼应，当主句动词是现 在时，从句根据自身的句子情况，而使用不同时态。
I know (that) he studies English every day. （从句用一般现在时）
I know (that) he studied English last term. （从句用一般过去时）
I know (that) he will study English next year. （从句用一般将来时）
I know (that) he has studied English since 1998. （从句用现在完成时）
当主句动词是过去时态（could, would除外），从句则要用相应的过去时态，如一般过去时，过去进行时，过去将来时等；当从句表示的是客观真理，科学原理，自然现象，则从句仍用现 在时态。
The teacher told us that Tom had left us for America．
All of us know that the moon moves round the earth.
6. think, believe, imagine, suppose等等动词引起的否定性宾语从句中，要把上述主句中的动词变为否定式。即将从句中的否定形式移到主句中。
We don’t think you are here. 我们认为你不在这。
I don’t believe he will do so. 我相信他不会这样做。
表语从句
在复合句中，位于系动词之后作表语的从句叫表语从句。引导表语从句的关联词与引导主语从句的关联词大致一样，表语从句位于连系动词后，有时用as if引导。
其基本结构为：主语+ 联系动词+ that从句
1.that 引导表语从句，无词义，只起连接作用，不可省。
2.联系动词可为be,look,seem,sound,appearwhether是什么意思等。
3.主语可为名词fact,truth,cause,question,explanation,trouble,assumption,belief等，代词this,that,these,it等。
The fact is that we have lost the game. 事实是我们已经输了这场比赛。
That’s just what I want. 这正是我想要的。
This is where our problem lies. 这就是我们的问题所在。
That is why he didn’t come to the meeting. 那就是他为什么不到会的原因。
It looks as if it is going to rain. 看上去天要下雨了。
Raw material is what we are badly in need of.原材料是我们所急需的。