强调句的用法
当句子中的主语、宾语、状语需要强调时，可以使用强调句型。强调句型的结构为：“It is (was) + 被强调部分 + that (which, who, whom) + 句中其他部分”。动词be的时态可随that从句的时态的变化而变化。例如：
It is the bag that costs 300 dollars. (强调主语)
It was three books that he read in the library yesterday. (强调宾语)
It was yesterday that I met him in the street. （强调时间状语）
使用此句型时，应注意以下几点：
1. 当被强调的部分指人时，要用who或that。当被强调的部分是宾语，又是指人时，要用whom或that，但通常多用that。
It was a young scientist who (that) solved this problem five years ago.（强调主语）
正是一位年轻的科学家五年前解决了这个问题。
It was Li Ming whom (that) I met at the railway station last week. (强调宾语)
上个星期我在车站遇到的人正是李明。
2. 当被强调部分指物时，只用that。
It is a new bike that his brother wants to buy.
他兄弟想买的正是一辆新自行车。
It was the legislature that played the decisive role in declaring war.
正是立法机构在宣战时起决定性作用。
3. 当被强调的部分是状语时，只能用that，不能用when或where。
It was because her mother was ill that she didn’t go with us.
正是因为她母亲病了，她才没有和我们一起去。
It was in the library that he borrowed that novel.
正是在图书馆里他借了那本小说。
4. 当被强调的部分是主语时，句子的谓语动词要和被强调的主语保持一致。
It is he who is late.
正是他迟到了。
It is they that were late.
正是他们迟到了。
5. 一般疑问句的强调句型为：“Is (was) it that…”；特殊疑问句的强调句型为：“特殊疑问词+is (was) it+that…?”。
Was it ten years ago that his father died?
他的父亲是十年前去世的吗？
When is it that you will go to Shanghai?
你到底什么时候去上海？
6. “not…until…”句型的强调结构为“It is not until…that…”，应注意把否定词not 转移到until前面。
普通句：He didn't go to bed until his wife came back.
直到他妻子回来他才睡觉。
强调句：It was not until his wife came back that he went to bed.
普通句：I didn’t know the news until yesterday.
直到昨天我才知道这个消息。
强调句：It was not until yesterday that I knew the news.
7. 强调句中的be前可用表推测的情态动词：must, can, may等。
It must be Piney that sent us this present.
肯定是Piney 给我们寄来了这件礼物。
How can it be that he didn’t pass the exams?
他考试没有通过怎么可能呢？
8. 强调句型不用于强调谓语、表语、since, as等引导的原因状语从句。如：
He is better today since he can walk around without my help.
他今天好些了，因为没有我的帮助他也可以四处走走了。
此句就不能有下列强调形式：
It is better today that he is today since he can walk around without my help. (错)
It is since he can walk around without my help that he is better today. (错)