It强调句型和祈使句表条件句型的基本构成
It强调句型
强调句的基本构成：It is/was + 被强调的部分 + who(主要指人时)/that + 其余部分
[注意1]
这种结构可以强调句子的主语、宾语、状语(包括时间，地点，方式，原因等)，但是不能强调谓语动词(参考句型15)。
原句的谓语动词如果是现在或将来时态，用It is…that/who….;
原句的谓语动词如果是过去时态，用It was…that/who….;
强调时间、地点、原因或方式时不要用when, where或how, 必须用that。
[例句1]
I saw him in the street yesterday afternoon.
→It was I who saw him in the street yesterday afternoon.(强调主语)
→It was in the street that I saw him yesterday afternoon.(强调地点状语)
→It was yesterday afternoon that I saw him in the street.(强调时间状语)
→It was him that/who I saw in the street yesterday afternoon.(强调宾语)
[例句2]He didn't go to bed until his mother came back.
→It was not until his mother came back that he went to bed.
[例句3]
Only when you nearly lose someone do you fully realize how much you value him.
→It is only when you nearly lose someone that you fully realize how much you value him.
只有你快要失去某个人时，你才意识到你是多么尊重他。
[例句4]
I was late again because the traffic was very heavy during the rush hour.
→It was because the traffic was very heavy during the rush hour that I was late again.
(强调句中只能强调由because引导的原因状语从句，because不能换成since, as, for, now that等)
[注意2]强调句的疑问结构
一般疑问句 Is / Was it +被强调部分 +who / that …?
特殊疑问句特殊疑问词+is /was +it +who / that…?
What is/was it that…? Who is/was it that…? When is/was it that…?
Where is/was it that…? Why is/was it that…? How is/was it that…?
[例句1]
I saw him in the street yesterday afternoon.
→When was it that you saw him in the street?
→Who was it that you saw in the street yesterday afternoon?
→Where was it that you saw him yesterday afternoon?
[例句2]
I don't know when he will come back.
→I don't know when it is that he will come back.(宾语从句疑问词后用陈述句语序)
-How was it that you got in touch with Mr. Smith? 你是怎么和Smith先生联系上的?
-Trough a friend of mine. 通过一个朋友。
祈使句表条件句型
(1)祈使句(表条件)+ or/or else/ otherwise + 主句(表结果)… "否则…，要不然…"
(2)祈使句(表条件)+ and +主句(表结果)
[例句]
Hurry up, or you'll be late for class.
Think it over and you will find the answer.
Give him an inch and he will take a mile. 得寸进尺。
Work hard and you will make progress every day. 好好学习，天天向上。
