what引导的主语从句

4. …as the earth cooled down, water began to appear on its surface.
随着地球的冷却, 地球的表面就开始
出现了水。
1) cool down 变凉, 冷却
2) appear “出现,似乎”是不及物动词 当表示 “似乎,好像”时是系动词,该 词无被动语态。
Language points
1. What it was to become was uncertain until between 4.5 and 3.8 billion years ago when the dust settled into a solid globe. What is even more important is that as the earth cooled down, water began to appear on its surface. [考点] what引导的主语从句，第一句what 在从句中作become 的宾语，第二句what在 从句中作主语。
② whether引导的从句一般不可以为 否定结构(选择问句的后一部分除 外);而if则可以跟否定结构,如: I don’t care if she doesn’t come. I don’t care if it doesn’t rain.
但是,在某些动词或形容词之后,则可
以用whether引导一个否定结构的句子
3. They were in time to produce the water... in time: sooner or later; eventually; I’ll see him in time. in time (for sth. /to do sth.): not late She will be back in time to prepare dinner.
d. look, seem 能与介词 like 构成习语， 意思是“看上去象”, 而 appear 却 不能。例如: It seems like years since I last saw you . 自从上次见到你后,好像很久没 有见到你了。 He looks like a student. 他看起来象个学生。
,这种结构往往表示肯定的含义,如：
I wonder whether he doesn’t think
too much of himself. 其意思相当于:I think he does think too much of himself.
③ 在个别动词之后, 如discuss 等, 只跟
用whether引导的宾语从句, 如: They discussed whether they should close the shop. We discussed whether Mary could join us.
与time相关的短语: in no time 立刻,马上 at times 有时 at a time 每次;依次 once upon a time 从前 on time 按时;准时 at one time 从前 for the time being 暂时 from time to time 不时地
[考例1] _____ was most important to her, she told me, was her family.（山东 2008） A. It B. This C. What D. As [点拨]选C。what引导主语从句，并在 从句中作主语。若选it则应去掉第二个 is；as引导定语从句，若选as则应去掉is that。
She hasn’t decided whether to go
or not.
•
引导主语从句 (包括从句在句首的 位置) 应当用whether, 不用if, 如： Whether it is true remains a
problem.
Whether he will come, I am not
sure.
The naughty boy ___ to me that the hen that ___ there just now had___ two eggs the day before. A. laid; laid; laid C. lied; laid; lain B. laid; lay; lain D. lied; lay; laid D
accident . 好像出了一次事故。
5. …by laying eggs. lay-laid-laid-laying 放, 把...... 放在 ......; 产卵 He laid his books on the desk. 注意: lay (laid; laid; laying) 放置;产卵 lie (lay; lain; lying) 躺;位于 lie (lied; lied; lying) 说谎
She is fifty but she appears young. 她五十岁了,但看起来很年轻。(其实 并非如此) Se seems young. (I think he is rich.) 她看起来很年轻。(根据个人的主观判 断而推断出) She looks young. 她很年轻。(从他外 表可出感觉出)
散发到太空中去。
阅读下列句子, 注意prevent ... from的 意思和用法。 1. There was nothing to prevent her from doing so. 2. We must prevent the water from being polluted. 3. The emperor ordered his porters to prevent the speaker entering the building.
2. The earth became so violent that it was not clear whether the shape would last or not. 1) violent 猛烈的，激烈的 2) whether可以引导主语从句、表 语从句、宾语从句和同位语从句; 而if只能引导宾语从句。
[归纳] prevent ... from的意思是 ____________________________。from 制止、阻止、使……不做某事 后多跟动词-ing形式(句1、句2)；有时可 省略from(句3)。 [拓展] 近义短语有: stop ... from 阻止…… 干某事; keep ... from 阻止……干某事。 注意: prevent和stop后的from都可以省略, 而keep ... from 中的from则不能省略，如 果省略了, 其意义将发生改变。
从句,而 look 不能。 It seems / appears that we won’t finish this work today. 我们好像今天完不成这项工作。
g. appear 和 seem 可用于there be 结
构中,而 look 不能。如:
There appears to have been an
④ whether 可以引导从句作介词的
宾语,而if则不能,如：
I’m not interested in whether
they’ll go or not.
⑤ whether可以直接跟动词不定式连
用,而if则不能, 如:
I didn’t know whether to laugh or
to cry.
一般不能。
He is looking very happy.
他现在看起来很高兴。
c. appear 和 seem 之后可接动词不定 式的一般式、完成式以及其他形式, 而 look 之后除了能接to be 结构外,不 接其它动词不定式形式。 She appeared to agree with you. 他好像同意你的意见。 They don’t seem to have read this novel. 他们好像没有读过这本小说。
值得注意的是：
① whether 和if都可以和or not连
用,但是whether之后可以直接
跟or not,而if则不能,如： I don’t care whether or not
your car breaks down.
I don’t know whether or not he’s coming. 但是不可以说： I don’t care if or not your car breaks down.
• 引导宾语从句既可以用whether, 也可以用if,两者常可以互换。 He asked me whether / if I could lend him my bike. Could you tell us whether / if it
snows in winter in Austr._________ we’ll go camping Whether tomorrow depends on the weather. 2. I have just discuss ________ we whether
should give him enough help. 3. They had no idea ________ or whether not they could achieve their goals.
•
引导表语从句用whether,不用if, 如: The question is whether you should accept it. The question is whether he will speak at the meeting.
•
引导同位语从句用whether,不用if,如: The question whether he’ll attend the meeting is essential. I am in doubt whether I should agree to the plan.