I.要点
1、it的用法
(1)用作人称代词，代替前文提到的无生命的事物，动植物、婴儿及指示代词this, that，如，
I have a new pen. It is beautiful.
The Browns have a new baby. It's cute.
(2)用来表示时间、天气、距离等，如，It's twelve o'clock now.
It's fine today.
(3)用作引导词，代替由不定式，ing形式或从句表示的真正的主语或宾语，如，
It's no good telling him that.
It's necessary for you to do so.
(4)用在强调结构中，构成强调句式：It is/was +被强调部分+that/who/whom +句子其余部分，可强调除谓语以外的句子其他成分，如，
It was this morning that I saw him in the street.
It was I who saw him in the street this morning.
It was in the street that I saw him this morning.
It was him whom I saw in the street this morning.
2、there be句型
英语表示某时某处或某物时，常用there be句型，这是一种倒装结构，如，
There are a lot of students playing on the ground.
There is going to be a test this afternoon.
当主语有两个或两个以上时，动词be常和最近的那个主语取得一致，如，
There is a pen and three pencils in the pencil-box.
There isn't a desk, a bench and three chairs in the room.
There are lots of people like it, aren't there?
there be句型，谓语动词除be之外，还可用其他表示存在，位置移动等意义的不及物动词或词组，如exist, stand, lie, enter, come, happen to be, appear to be等，如，
There stands a house at the foot of the hill.
there be句型表示"存在"而have表"有"、"拥有"，所以there be中 be不能换成have，但当have表示事物的特征时，可用"主语+have"结构替换there be 句型，如：
There are five doors in the house.
The house has five doors.
there be 的其它句型：
1、There must be a meeting in the office.
2、There have been great changes since 1979.
3、There being no bus, we had to walk home.
I. 例题
例1 ____ that he went to sleep.
A It was until midnight B That was until midnight
C It was not until midnight D That was not until midnight
解析：该题答案为C。强调until结构时，要将否定词not移到until前。又如：He didn't leave until twelve 改为It was not until twelve that he left.
例2 There are a lot of students ____ in the class room.
A talk B talking C talked D to talk
解析：该题正确答案为B。 There be句型为倒装句，可换为A lot of students are talking in the class room. 又如：There is a lot of noise heard out in the street.
