語法復(fù)習(xí)五：強調(diào)句、It的用法、省略和插入語
一、強調(diào)句
（一）強調(diào)句句型
1、陳述句的強調(diào)句型：it is/ was + 被強調(diào)部分（通常是主語、賓語或狀語）+ that/ who（當(dāng)強調(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、特殊疑問句的強調(diào)句型：被強調(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、強調(diào)句例句：針對i met li ming at the railway station yesterday.句子進行強調(diào)。
強調(diào)主語：it was i that (who) met li ming at the railway station yesterday.
強調(diào)賓語：it was li ming that i met at the railway station yesterday.
強調(diào)地點狀語：it was at the railway station that i met li ming yesterday.
強調(diào)時間狀語：it was yesterday that i met li ming at the railway station.
5、注意：構(gòu)成強調(diào)句的it本身沒有詞義；強調(diào)句中的連接詞一般只用that, who，即使在強調(diào)時間狀語和地點狀語時也如此，that, who不可省略；強調(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行時，用it was … ，其余的時態(tài)用it is … 。
（二）not … until … 句型的強調(diào)句
1、句型為：it is/ was not until + 被強調(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）謂語動詞的強調(diào)
1、it is/ was … that … 結(jié)構(gòu)不能強調(diào)謂語，如果需要強調(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）要小心啊！
2、注意：此種強調(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）