it是形式主语吗？为什么不选C it形式主语的句子结构
形式主语it的用法
It
作形式主语常见句型
1.It + be +
形容词
+ that-
从句
可用于此句型的形容词有
: wonderful, true
，
good
，
right
，
wrong
，
（
un
）
important
，
useless
，
surprising
，
disturbing,frightening,alarming,clear
，
unusual
，
lucky
，
certain, necessary
等。
如：
①
It is quite certain that he will be at the meeting.
他将出席会议是无疑的。
②
It is surprising that he came late to school this morning.
他今天早上迟到真令人惊讶。
③
It is important that we (should) study hard.
我们努力学习是很重要的。
注意
:
该句型中的形容词是
（
un
）
important, necessary
等时，
从句应为
(should )+
动词原
形。
It is important that we (should) learn English well.
It is necessary that he (should) remember these words.
2.It + be +
名词
+ that-
从句
适用该句型的名词
（词组）
有
: a pity
，
an honor
，
a good thing
，
a fact
，
a surprise
，
a question,
a shame,a custom, a truth,our hope, no wonder, good/bad manners
等。如：
①
It is a pity (that) you missed the sports meeting last week.
你错过了上周的运动会太
可惜了。
②
It is a fact that English is being accepted as an international language.
事实上英语已经
被作为一种国际语言而接受了。
3. It
＋
seem
／
appear
／
happen
的适当形式＋
that
从句。
①
It seems that there is a big waste pipe coming down from the town.
②
It appeared that he was calm, but inside his heart was beating wildly with fear.
4. It + be +
过去分词
+
主语从句，这类过去分词有：
announced, believed, expected, hoped,
decided, reported, said, shown
等，
如：
It is reported that 16 people were killed in the earthquake.
It is not decided who will give the operation to the patient.
5. It is time ( about time ,high time ) that ...
该句型中
that
后的从句应该用虚拟语气，值得注意的是①
常用过去时态表示虚拟．②
有时也用
should +
动词原形，
should
不能省。常译为＂是（正是）
．
．
．的时侯．
．
．＂。
It is time that children should go to bed.
= It is time that children went to bed.
6. It is the first ( second ... ) time that ...
用完成时态。至于用什么完成时态，
由主句的谓语动词的时态决定。如果是一般现在时，后
面从句用现在完成时态；
如果是一般过去时，
后面从句则用过去完成时态。
该结构中
that
可
以省去；
it
有时用
this
替换．常译为＂是第一（二）
．
．
．次．
．
．＂。
It is the first time I have been here.
= This is the first time I have been here.
7. It + be + adj./ n. (for sb. / of sb.) + to do sth.
该句型中的形容词通常是表示事物的特点或
特征的如
difficult
，
hard
，
easy
，
impossible
，
necessary
，
important
等，此时用
for
；或表示人
的性格特征或特点的如
nice
，
good
，
bad
，
kind
，
silly
，
foolish
，
wise
，
clever
，
careless
，
rude
，
brave
，
cruel
，
careful
，
grateful
等，这时要用
of
。如：
①
It is foolish of you to give up such a good chance.
②
It is necessary for college students to master at least a foreign language.
it在名词性从句中形式主语
it作形式主语,形式宾语的用法
☺ it 作形式主语
1.他犯了那样一个错误真是遗憾.
That he made such a mistake is a pity .
It is a pity that he made such a mistake.
It is well known/reported/ thought/said that…
It is clear/necessary/certain/true that…
It is a pity/a shame/an honor that…
It doesn’t matter whether…
It seems that…
It happens that…
1.____is known to all,Taiwan is only part of China.
A.As B.That C.Which D.What
it形式主语
例：It is wrong to treat an old lady like this.
It is no use arguing with him.
It 作形式主语的常见句型：
① It + be + 形容词 + to do sth. / doing / that ….
it在定语从句中能做形式主语吗
it作形式主语 代替的是不定式动名词或从句。所以在定语从句中很少有it作形式主语的现象。但从理论上讲 定从中可以有it作形式主语。如this is the book which it is important for me to have.（which代替先行词引导定从并作从句中to have 的宾语。如果改成which is important for me to have则意思不一样。）这是 我拥有此非常重要 的那本书。