1. It is/ was obvious/ clear/ true/ possible/ certain...that...

......是明显/清楚/真的/可能/肯定的。

　　这是主语从句最常见的一种结构。句中it作先行词，代替名词性从句。该结构中的名词性从句可用that, what, when等引导。

It is obvious that she is very clever.

很明显，她挺聪明的。

It is not certain what caused the accident.

还不肯定那个事故是什么引起的。

It isn't remotely possible that you will be chosen to go.gkstkgkstkgkstk]

挑选你去的可能性并非很小.。

　　it作形式主语代替从句的句型还有：

① It is+n.+that-clause

② It is+过去分词+that-clause

③ It is+ vi.+that-clause

It's natural that teachers are strict with their students.gkstkgkstkgkstkgkstk]

老师对学生要求严格是很自然的事。

It's obvious that this destruction will become more dangerous in the future. 【一讲一练】

单项选择。

1. It has been proved _____ eating vegetables in childhood help stop protecting you against serious illness in later life.

A. if B. because

C. when D. that

2. It is by no means clear _____ the president can do to end the strike.

A. how B. which

C. that D. what

【答案】

1. D 2.D

【解析】

1. 句子为主语从句，it是形式主语。句意：实践证明小时候多吃蔬菜有助于在后来的生活中帮助你抵抗疾病。

2. 考查名词性从句的引导词。句中it是形式主语，空后的从句为真正的主语;主语从句中缺少do的宾语，故选择what 作为主语从句的引导词且充当从句中谓语动词do的宾语。

很明显这种破坏在未来会变得更加危险。

It is suggested that we ( should ) discuss the problem.gkstkgkstkgkstk.Com]

有人建议我们应该讨论一下这个问题。

It appears/seems that they will win the game.

他们似乎要赢得这场比赛。

2. While she was on earth she met the herd boy Niulang and they fell in love. 她在人间遇到了牛郎，两人相爱了。

gkstkgkstkgkstk]

　　句中While she was on earth作时间状语，其中while表示"当......的时候"。

He fell asleep while(he was)watching TV.

他在看电视的时候睡着了。

Mary made coffee while her guests were finishing their meal.

客人们就要吃完饭的时候，玛丽去煮咖啡了。

while的不同含义：

(1)只要

While there is life, there is hope.

只要有生命就有希望。

(2)但是，可是，表对比转折

We know usually women stay at home and do all the housework while men go out to work.

我们知道，通常女人们在家里做家务，而男人们则外出工作。

(3)虽然，尽管

While I understand what you say, I can't agree with you.

尽管我明白你的话，但我还是不同意。 【名言警句】

The first step is as good as half over.

第一步是最关键的一步。

Sow nothing, reap nothing.

春不播，秋不收。

单项选择。

1. In some places women are expected to earn money _____ men work at home and raise their children.

A. but　　　　　 B. while

C. because D. though

2. ______ I accept that he is not perfect, I do actually like the person.

A. While B. Since

C. Before D. Unless

【答案】

1. B 2. A

【解析】

1. while在句中表示对比转折，意思是"但是，可是"。句意为，在某些地方，女人负责挣钱，而男人负责家务和孩子。

2. 这里的while表示让步，意思是"虽然，尽管"。句子的意思是，尽管我承认他不够完美，但是我确实很喜欢他这个人。