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
一、It 与高考题
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. 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 ?
A. this B. that C. he D. it
4）It worried a bit her hair was turning grey .
A. while B. that C. if D. for
答案1） — 4）DDDB。
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。
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 .