一、強(qiáng)調(diào)句
（一）強(qiáng)調(diào)句句型
1、陳述句的強(qiáng)調(diào)句型：It is/ was + 被強(qiáng)調(diào)部分（通常是主語、賓語或狀語）+ that/ who（當(dāng)強(qiáng)調(diào)主語且主語指人）+ 其它部分。
e.g. It was yesterday that he met Li Ping.
2、一般疑問句的強(qiáng)調(diào)句型：同上，只是把is/ was提到it前面。
e.g. Was it yesterday that he met Li Ping?
3、特殊疑問句的強(qiáng)調(diào)句型：被強(qiáng)調(diào)部分（通常是疑問代詞或疑問副詞）+ is/ was + it + that/ who + 其它部分？
e.g. When and where was it that you were born?
4、強(qiáng)調(diào)句例句：針對I met Li Ming at the railway station yesterday.句子進(jìn)行強(qiáng)調(diào)。
強(qiáng)調(diào)主語：It was I that (who) met Li Ming at the railway station yesterday.
強(qiáng)調(diào)賓語：It was Li Ming that I met at the railway station yesterday.
強(qiáng)調(diào)地點狀語：It was at the railway station that I met Li Ming yesterday.
強(qiáng)調(diào)時間狀語：It was yesterday that I met Li Ming at the railway station.
5、注意：構(gòu)成強(qiáng)調(diào)句的it本身沒有詞義；強(qiáng)調(diào)句中的連接詞一般只用that, who，即使在強(qiáng)調(diào)時間狀語和地點狀語時也如此，that, who不可省略；強(qiáng)調(diào)句中的時態(tài)只用兩種，一般現(xiàn)在時和一般過去時。原句謂語動詞是一般過去時、過去完成時和過去進(jìn)行時，用It was … ，其余的時態(tài)用It is … 。
（二）not … until … 句型的強(qiáng)調(diào)句
1、句型為：It is/ was not until + 被強(qiáng)調(diào)部分 + that + 其它部分
e.g. 普通句：He didn’t go to bed until/ till his wife came back.
強(qiáng)調(diào)句：It was not until his wife came back that he went to bed.
2、注意：此句型只用until，不用till。但如果不是強(qiáng)調(diào)句型，till, until可通用；因為句型中It is/ was not … 已經(jīng)是否定句了，that后面的從句要用肯定句，切勿再用否定句了。
（三）謂語動詞的強(qiáng)調(diào)
1、It is/ was … that … 結(jié)構(gòu)不能強(qiáng)調(diào)謂語，如果需要強(qiáng)調(diào)謂語時，用助動詞do/ does或did。
e.g. Do sit down. 務(wù)必請坐。
He did write to you last week. 上周他確實給你寫了信。
Do be careful when you cross the street. 過馬路時，務(wù)必（千萬）要小心??！
2、注意：此種強(qiáng)調(diào)只用do/ does和did ，沒有別的形式；過去時用did ，后面的謂語動詞用原形。
二、It的用法
（一）作人稱代詞
1、it代替前面（或后面）的單數(shù)名詞或分句等所表示的事物。
e.g. You cannot eat your cake but have it.（it代替前面的cake）
Although we cannot see it, there is air all around us. （it代替后面的air）
They say he has left town, but I don’t believe it. （it代替前面They…town分句中的情況）
2、代替有生命但不能或不必分陰陽性的東西（包括嬰兒）。
e.g. Yesterday we saw a big tree. It was fully twenty metres high. （it代替前面的tree）
The baby cried because it was hungry. （it代替前面的baby）
3、在某些習(xí)慣說法中，可以代替人。
e.g. ---- Someone is knocking at the door, Peter. ---- Who is it? ---- It’s me.
---- Who are singing? ---- It is the children.
---- The light is still on in the lab. It must be the third-year students doing the experiment.
4、it與one的區(qū)別：這兩個詞都可以代表前面說過的名詞，但it用于同名同物的場合；one則用于同名異物的場合。
e.g. ---- Do you still have the bicycle? ---- No, I have sold it.
---- Is this knife yours? ---- No. It is Xiao Zhang’s. Mine is the one on the desk.
5、it與that的區(qū)別：兩詞都可代替某一特定名詞，但that指同一類，并非同一個。
e.g. The climate of South China is mild（溫和的）; I like it very much.（it指the climate of South China）
The climate of South China is much better than that of Japan.（that指the climate）
（二）作無人稱代詞
it作無人稱代詞時，除了句中找不到它所代表的詞語外，另一個特點是它后面的內(nèi)容都是表示天氣、時間、距離、度量衡及情況等。
It is fine (rainy, windy, etc.).
It is noon.
It is a half hour’s walk to the factory.
It is eighteen square metres in area.
What does it matter?
（三）作強(qiáng)調(diào)詞，構(gòu)成強(qiáng)調(diào)結(jié)構(gòu)
用以幫助改變句子結(jié)構(gòu)，使句子的某一成分受到強(qiáng)調(diào)。“It is (was) + 所強(qiáng)調(diào)的成分 + that (who) + 其它成分。”在這個句型中，it本身沒有詞義。詳見“一、強(qiáng)調(diào)句”。
（四）引導(dǎo)詞it作形式主語（賓語）
為了使句子平衡，常采用形式主語（或賓語）it ，而把真正的主語（或賓語）置于句子后面。通常引導(dǎo)詞it與它所代替的句子成分中間要夾有某些詞。
e.g. It takes half an hour to go there on foot.（It與to go there on foot之間夾有takes half an hour四個詞）
We thought it strange that Mr Smith did not come last night. （it與that從句中間夾有 strange）
但有時it與所替代部分之間并不夾有其它詞。
e.g. You may depend on it that they will support you.（因為介詞on之后一般不直接接that引導(dǎo)的賓語從句。注意：it不是多余的，不能當(dāng)作錯句）
