高二英語選修三第二單元知識點
學習是一個堅持不懈的過程，走走停停便難有成就。比如燒開水，在燒到80度是停下來，等水冷了又燒，沒燒開又停，如此周而復始，又費精力又費電，很難喝到水。以下是小編給大家整理的高二英語選修三第二單元知識點，希望大家能夠喜歡!
高二英語選修三第二單元知識點1
一、引導主語從句的連詞主要有：
從屬連詞：that whether
連接代詞：who whoever whom whose what whatever which whichever
連接副詞：when where how why
二、用法
主語從句是在復合句中充當主語的從句，通常放在主句謂語動詞之前或由形式主語it代替，而本身放在句子末尾。
1. It 作形式主語和it引導強調句的比較
①主語從句常用it作形式主語，一般常用句型為：It is+{名詞/形容詞/過去分詞}+主語從句例如：
It is still a question whether she will come or not.
It is strange that you should like him.
It is still unknown which team will win the match.
另外，還有一些比較多見的結構：
It turned out that……;
It has been proved that……;
It happened/occurred that……;
It is well-known that……等等
②而強調句則不同，它的結構是：It+be+被強調部分+that+從句
強調主語：It is the times that produce their heroes.時勢造英雄
強調賓語：It is English that Prof.Lin teaches us.
強調狀語：It was in shanghai that I saw the film.
判斷是否是強調句有一個方法，就是將that以后的“句子的其余部分”拿出來單獨看，看有沒有缺成分，缺的是什么成分，再把謂語動詞后面that前面的那部分，帶到你認為缺成分的地方，如果放進去是一句完整的句子了，那就說明是強調句。
2. 用it 作形式主語的結構
(1) It is +名詞+that從句
It is a fact that … 事實是……
It is an honor that …非常榮幸
It is common knowledge that …是常識
(2) it is +形容詞+that從句
It is natural that… 很自然……
It is strange that… 奇怪的是……
(3) it +不及物動詞+that從句
It seems that… 似乎……
It happened that… 碰巧……
(4) it is+過去分詞+that從句
It is reported that… 據報道……
It has been proved that… 已證實……
3.主語從句不可位于句首的五種情況
(1) if引導的主語從句不可居于復合句句首。
(2) It is said , (reported) …結構中的主語從句不可提前。例如：
It is said that President Jingo will visit our school next week.
(3) It happens…, It occurs… 結構中的主語從句不可提前。例如：
It occurred to him that he failed in the examination.
(4) It doesn’t matter how/whether …結構中的主語從句不可提前。例如：
It doesn’t matter whether he is wrong or not..
(5) 含主語從句的復合句是疑問句時，主語從句不可提前。例如：
Is it likely that it will rain in the evening?
4. What 與that 在引導主語從句時的區別
What 引導主語從句時在從句中充當句子成分，如主語.賓語.表語，而that 則不然。例如：
What you said yesterday is right.
三、賓語從句用以區分主語從句的幾個特征
1、引導詞：what which whose when whet herif where
2語序：賓語從句必須是用陳述語句。(名詞性從句都是陳述語序)
如：I think that you must work harder.
賓語從句的引導詞、連接詞的區別、否定轉移等現象。
補充：從句的語序永遠是陳述句。
高二英語選修三第二單元知識點2
【First aid知識點】
1. first aid 的意思是“急救”，例如：first aid to the injured 給予傷員的急救。
短語聯想：
give/offer aid 援助 come to sb's aid 幫助某人
teaching aids 教具 medical aid 醫療救護
with the aid of 借助于
get injured 受傷，在現代英語中大量地出現了由“get + 及物動詞不達意的過去分詞”構成的被動語態，這叫 get - 型被動語態。又如：
The computer got (was)damaged when we were moving. 我們搬家的時候，電腦碰壞了。
高二英語選修三第二單元知識點3
Worried about the journey, I was unsettled for the first few days.
Well-known for their expertise, his parents’ company …..
Confused by the new surroundings, I was hit by the lack of fresh air.
Exhausted, I slid into the bed and fell fast asleep.
過去分詞作狀語：過去分詞作狀語時，說明動作發生的背景或情況，其等同于一個狀語從句。vt 過去分詞作狀語時與主句主語構成被動關系，表示被動和完成，vi 過去分詞表示狀態或動作的完成。
Heated , water changes into steam .
The professor came in, followed by a group of young people .
1 作原因狀語，等于as / since / because 引導從句
Moved by what she said ,we couldn’t help crying . = ( As we are moved by what she said …
2 作時間狀語，等于when 引導時間從句，如果分詞表示的動作與謂語的動作同時發生，可在分詞前加when/ while / until 等使時間意義更明確。
When heated , water can be changed into steam .
Seen from the hill ,the park looks very beautiful .= ( When the park is seen from the hill…
3 作條件狀語等于 if / whether 引導從句
Given more attention , the cabbages could have grown better .= ( If they have been given more attention ….
Compared with you , we still have a long way to go = ( If we are compared with you
4 作方式或伴隨狀語
The actress came in , followed by her fans .
She sat by the window , lost in thought .
5 作讓步狀語
Much tired ,he still kept on working .=(Although he was tired ,) he ….
6 獨立主格結構： 當分詞的邏輯主語不是主句主語時，分詞可以有自己獨立的邏輯主語，這種結構稱為獨立主格結構。常用來表示伴隨情況。
The boy rushed into the classroom , his face covered with sweat .
All things considered ,your article is of great value than hers .
Rewrite with proper conjunctions
Example : United we stand, divided we fall.
If we are united, we will stand, but if we are divided,we will fall.
1 Asked what had happened, he told us about it.
→When he was asked what had happened, …
2 Well known for his expert advice, he received many invitations to give lectures.
→Because he was well known for his expert advice, …
3 Given more time, we would be able to do the work much better.
If we were given more time,
4 Once translated into Chinese, the book became very popular among Chinese teenagers.
Once it was translated into Chinese,
5 Deeply interested in medicine, she decided to become a doctor.
Because she was deeply interested in medicine,
6 Left alone at home, Sam did not feel afraid at all.
Although he was left alone at home,
現在分詞與過去分詞作狀語
現在分詞作狀語時，與其邏輯主語之間是主動關系，;而過去分詞與其邏輯主語之間則表示被動關系。
Seeing these pictures, I couldn’t help thinking of those days when I was in Beijing . Seen from the top of a thirty-storeyed building, Beijing looks more magnificent. (see)
選擇現在分詞還是過去分詞，關鍵看主句的主語。如分詞的動作是主句的主語發出，分詞就選用現在分詞，反之就用過去分詞。例如：
Used for a long time, the book looks old.
由于用了很長時間，這本書看上去很舊。
Using the book, I find it useful.
在使用的過程中，我發現這本書很有用
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