4. Was it in this palace the last emperor died ?
A. that B. in which C. in where D. which
〖答案与简析〗选A。测试it 用在强调结构中，为了强调句子的某一成分（通常是主语、宾语或状语），常用强调It is (was) + 被强调成分 + that(或who）…。被强调部分指人时用 that 或 who ，在其它情况下（包括强调时间或地点状语）用that 。又如：
1）Was it during the Second World War he died ? (MET 88）
A. that B. which C. in which D. then
2) It was not she took off her dark glasses I realized she was a famous film star .
A. when ; that B. Until ; that C. until ; when D. when ; then
答案 1) A 2) B。
3. I don't think possible to master a foreign language without much memory work .
A. this B. that C. its D. it
〖答案与简析〗选D。测试 it 用作形式宾语，代替由不定式、动名词或从句表示的真正宾语。当宾语有自己的补足语时，用it作形式宾语，真正宾语放在补足语之后。常用这种句型的动词有think , make , find , feel , consider 等。
2. Is necessary to tell his father everything ?
A. it B. that C. what D. he
〖答案与简析〗选A。测试 it 用作形式主语，代替由不定式（或不定式复合结构）、动名词或从句表示的真正主语。又如：
1）Is possible to fly to the moon in a spaceship ?
A. now B. man C. that D. it
2）Is necessary to complete the design before National Day ?
A. this B. that C. he D. it
3）Does matter if he can't finish the job on time ?
4）It worried a bit her hair was turning grey .
A. while B. that C. if D. for
答案1） ― 4）DDDB。
1. Tom's mother kept telling him that he should work harder , but didn't help .
A. he B. which C. she D. it
〖答案与简析〗选D。测试 it 用作人称代词，代替前文提到过的事物。又如：
1）― The light in the office is still on.
― Oh , I forgot .
A. turning it off B. turn it off C. to turn it off D. having turned it off
2）― Have you heard the news about Tom ?
― No , what ?
A. is it B. it is C. are they D. they are
3）If you don't know the word , why don't you in the dictionary ?
A. look at it B. look after it C. look up it D. look it up
答案1）― 3）CAD。值得注意的是，由动词和副词组成的短语动词用it 作宾语时，it 应置于动词和副词之间。
2. it 代替连接代词或连接副词引导的从句作形式主语。
1) It is known (not decided , not made clear , found out , discussed , being discussed , being considered , a question , uncertain等) + 连接代词或连接副词引导的从句。
It is still a question when we shall have our sports meet . 我们将什么时候举行运动会还是一个问题。
It is uncertain whether he can attend this conference or not . 他能否来开会还不能确定。
2) It doesn't matter(doesn't matter too much , doesn't make too much difference等) + 连接代词或连接副词引导的从句。如：
It doesn't matter whether we go together or separately . 我们一起去还是分开去都可以。
It doesn't matter too much to me what you do or where you go . 你做什么或去什么地方，对我都无关紧要。
【动脑动手】
单元能力立体检测
1. it 代替连词 that 引导的从句作形式主语。
1) it + be + 过去分词 + that 从句
It's said that Tom has come back from abroad . 据说汤姆已经从国外回来了。
It was reported that dozens of children died in the accident . 据报导，数十名儿童在事故中死亡。
可用于该句型的过去分词还有：known , thought , told , believed , hoped , announced ,expected , decided , suggested等，该句型常可以转换成含有宾语从句的复合句或者含有不定式作主补的简单句。如：
It's said that Tom has come back from abroad . →People say that Tom has come back from abroad . →He is said to have come back from abroad .
2) It + be + 名词词组 + that 从句
It's a pity that he can't swim for his age . 真遗憾，就他的年龄来讲，他竟不会游泳。
It's a wonder that you could finish such a hard task in such a short time . 真奇怪，你竟能在如此短的时间内完成艰巨的任务。
可用于该句型的名词词组还有：an honour , a good thing , a fact , a surprise , good news等。
3) It + be /seem + 形容词 + that 从句
It is likely that they will beat us tonight .今晚很可能他们会赢我们。
It doesn't seem that she will give us a hand .她帮我们的可能性似乎不太大。
可用于此句型的开容词还有；wonderful , true , good , right , wrong , (un)important ,useless , surprising , clear , possible , unusual , lucky , certain 等。
4) It + seem / appear / happen + that 从句
It seems that he enjoys pop songs very much .看来他非常喜欢流行歌曲。
It appears that Tom might change his mind .看来汤姆会改变主意。
It happened that I went out that day .碰巧我那天外出了。
注意，句型4可转换成含不定式的简单句。如上述句子可转换为：
He seems to enjoy pop music very much . / Tom appears to change his mind ./ I happened to go out that day.
6. It / This / That + the first(second , third …) time + that-clause
这个句型表示截止到说话时为止的某人的一种经历，关键是注意time前有序数词，主句是 is 时 ，从句要用现在完成时；如果主句用一般过去时was ，则从句须相应地用过去完成时。例如：
This is the first time (that) these Europeans have visited the Great Wall .
It was the fifth time (that) I had paid a friendly visit to Africa .
二、It代替从句作形式主语的常见句型
5. It + be + time + that-clause
这个句型属虚拟语气结构，不管主句中用的是 is 或 was ，that从句都须用动词的过去式或should + 动词原型(但不及用过去式普通)，在time之前有时可加上high或about 以加强语气。例如：
It is time(that)we handed in our exercises .(= It is time that we should hand in our exercises .)
It is high time (that ) she wrote a letter to her boyfriend .
4. It + be + 时间 + that-clause
这个句型是个强调句型。例如：
It was two years ago that he made an important invention .
(原句是：He made an important invention two years ago . )
It was at 5 o'clock that he practised playing the violin in the morning .
(原句是：He practised playing the violin at 5 o'clock in the morning . )
比较：It was 5 o'clock when he started in the morning .
(5 o'clock前没有介词，这是个定语从句)
3. It + be + 时间 + when-clause
这个句型中, it 指时间，而且表示时间的词语前没有介词(时间一般为具体时间)。主句中的谓语动词和从句中的谓语动词在时态上一般是一致的，主句是will be，when从句用一般现在时代替将来时。例如：
It was already 8 o'clock when we got home .
It was the next morning when we finished our work .
It will be midnight when they get there .