選B
IT 的用法
1.做代詞,代替剛提到的過(guò)的一件事情.
a.可以指一個(gè)具體的東西.b.可以指前面所談的事情或情況.
eg.a.It’s a nice room.
b.You promised to write the article,and you must do it.
2.做代詞代替指示代詞 this,that
eg.---What’s this?------ It’s a flag.
3.起指示代詞的作用,指一個(gè)人或事物,it 所指的東西不很具體.
a.有時(shí)指某個(gè)動(dòng)作的人.b .有時(shí)指引起某種情況的事物.
eg.a..----Who is knocking at the door?---- It’s me.
b.It’s the wind shaking the window.
4.指環(huán)境,情況等.
eg.It’s very quiet at the moment.
5.指自然現(xiàn)象（天氣,氣候,明暗等）
eg.I’s getting cold (dark,late,etc.).
6.指季節(jié),時(shí)間
eg.It was late autume (early spring,mid summer,etc).
7.指距離
eg.It’s only five miles (half an hour’s walk).
8.用于強(qiáng)調(diào)結(jié)構(gòu),在這里it 可以說(shuō)沒(méi)有意思.它只幫助改變一個(gè)句子的結(jié)構(gòu),使某一成分受到強(qiáng)調(diào),改變結(jié)構(gòu)的辦法是：
IT + be + 要強(qiáng)調(diào)的部分+ that(who,whom) + 句子其他部分
強(qiáng)調(diào)的部分是人用who(m),其他情況多用that
eg.It was Mary who (that) met your sister in the zoo yesterday.
It was your sister that (whom) Mary met in the zoo yesterday.
It was in the zoo that (where) Mary met your sister yesterday.
9.做形式主語(yǔ),代替一個(gè)由不定式,動(dòng)名詞短語(yǔ)或是從句表示的主語(yǔ),使原來(lái)的這些主語(yǔ)可以放在句子后部,避免頭重腳輕.
a.真正的主語(yǔ)是不定式.
Eg.It’s our duty to attend to this letter.
b.真正的主語(yǔ)是動(dòng)名詞.
Eg.It’s no use talking to him about it.
c.真正的主語(yǔ)是從句,這個(gè)從句可以用that 引起,也可以用一個(gè)連接代詞或連接副詞引起.
Eg.It happened that I wasn’t there that day.
It’s doubtful whether she will be able to come..
10.做形式賓語(yǔ),代替一個(gè)由不定式,動(dòng)名詞,或是賓語(yǔ)從句,往往把賓語(yǔ)放在它的補(bǔ)足語(yǔ)后面.而用it做形式賓語(yǔ),放在賓語(yǔ)補(bǔ)足語(yǔ)之前.
Eg.I think it no use arguing with him.