一、定語從句
引導定語從句的關係代詞有that,which,who（賓格whom），所有格whose）和關係副詞 where when why 等，關係代詞或關係副詞在定語從句中充當一個成分，關係代詞that，which,who,whom等在從句中分別作主語或賓語，whose在從句中作定語，而關係副詞when,where,why等在從句中作狀語。 如：
1.I will never forget the days when/in which we worked together.
2.I will never forget the days which/that we spent together.
解析：在句①中，表示時間的名詞the days在從句中充當的是狀語，所以用關係副詞when來代指，引導定語從句修飾先行詞the days；
而在句②中，表示時間的名詞the days在從句中充當的是動詞spent的賓語，所以用關係代詞that或which來代指。
同樣，表示地點或原因的名詞如果在從句中作狀語，則用關係副詞where 或why來代指；如果在從句中作動詞的賓語，則用which或that來代替。 如：
1.This is the factory where/in which I worked.（作狀語）
2.This is the factory that/which I visited years ago.（作賓語）
注：當先行詞為time,reason, place時，引導詞可以省略。如：
1.This was the first (when/what) I had serious trouble with my boss.
2.That is the reason (why) I did it.
3.This is the place (where) we met yesterday.
另外，定語從句中謂語動詞的數應與先行詞的數相一致。如：
1.Mr. Jackson is the only foreigner that is present at the party.
2.He is one of the students who were praised by the teacher.
解析：在句①中，先行詞foreigner被only修飾，強調只有一個，所以從句中謂語動詞用單數形式，而在句②中，who引導的定語從句修飾先行詞the students，為複數，所以從句謂語動詞應為複數。
二、名詞性從句中的易錯點
（一）that引導的定語從句與同位語從句
定語從句與前面的的名詞是修飾與被修飾的關係，“……的名詞”，而同位語從句是用來說明前面名詞的內容。與that從句同位的名詞必須是一些表示事實或概念的抽象名詞，如：
fact,news,belief,truth,reply等。
That在定語從句中必須作成分，可用which或who/whom代替，而that在同位語從句中不充當任何句子成分，只起連接作用。如：
1.Along with the letter was his promise that he would visit me this coming Christmas.
2.Do you still remember the chicken farm that we visited three months ago.
解析：在句①中，that引導同位語從句解釋說明promise的內容，that不充當任何句子成分，只起連接作用，而在句②中，that在其引導的定語從句中作動詞visited的賓語，對先行詞the chicken farm起修飾作用。
（二）名詞性從句中，關於it作形式主語和形式賓語的易錯點
1) 名詞性從句作主語或賓語時，為保持句子平衡，常用it作形式主語或形式賓語。如：
It's a pity that he don't come to give a speech.（形式主語）
We think it possible that you can finish the job today.（形式賓語）
2）謂語動詞 appreciate, dislike, hate, like, love, make等接由if或when 引導的賓語從句時往往在從句前加上形式賓語it. 例如：
I would appreciate it if you could come to my birthday party.
3）動詞hare, take, hide, punish, put等,後接由that 引導的病因從句式，往往在從句前加形式賓語it. 例如：
1.I take it that you will be leaving Shanghai soon.
2.we punished it that we had finished the project ahead of time.
4）短語動詞answer for, count on depend on, insist on, see to等後接有that引導的賓語從句時，必須冠以形式賓語it. 例如：
① I'm counting on it that you will come.
② She'll see to it that he goes ahead.
注：作形式主語和形式賓語時只能用it.
三、虛擬語氣
（一）虛擬語氣在if引導的條件句中的易錯點
1.If my lawyer had been here last Saturday, he would have prevented me from going.
2.If you had studied hard at school, you would be a college student now.
句子①②都是虛擬語氣在條件句中的使用，從句中都是假設過去的情況，所以用過去完成時，但在主句中，句①依然指代過去的情況，謂語動詞是would have done，而②中含有一個表示現在的時間狀語now, 這樣就必須將其理解為假設現在的情況，所以謂語動詞必須為would/should/might+動詞原形，學生在這一點上經常會忽略now的存在，從而按句①的形式填寫答案。
（二）虛擬語氣在名詞性從句中的用法
1.在“it is important (strange, natural, necessary……)+that”句子或者“It is decided (ordered,suggested, demanded, advised……)+that”句子中，主語從句中的謂語動詞常用（should）+動詞原形結構，表示某事“重要”、“必要”、“被決定”等
例如：
1.It is important that everyone (should ) obey the rules all day and all night.
2.It is decided that the meeting (should) be held tomorrow afternoon.
2. suggest, insist 後面指賓語從句時需注意的地方
1）suggest 當“建議”“提出”講時，其後賓語從句的謂語動詞常用“should+動詞原形”
例如：He suggested that the work (should) be started at once 他建議立即動工。
類似的動詞還有insist堅持，demand要求，desire要求、請求，request請求，require要求、需要，order命令，propose建議，command命令，ask要求，advise建議，prefer寧願等。 這些動詞變被動語態（如：It is suggested + that主語從句）形式後，主語從句謂語動詞仍用“（should）+動詞原形” 這些動詞變名詞（如suggestion）後，其後的表語從句和同位語從句中的謂語部分仍用“(should)+動詞原形”
2）suggest 當“提出（某看法），暗示，啟發”講時，其後賓語從句的動詞不用虛擬語氣。
例如：
(1)The police suggested that the thief might be one of the family member
警察局提出竊賊可能是一名家庭成員。
（2）Her yawns suggests that she is sleepy.
她打哈欠表明她困了。
(3)Although he didn't suggest that we __ the decision to swim across the river, but his look suggested that our decision __wrong.
雖然他沒提出我們應該終止遊過這條河的決定，但他的表情表明我們的決定是錯誤的。
A stop; was B should stop; be
C stopped;was D stopped; should be
在這個句子中，前一個suggest當“建議”“提出”講，而後一個作“表明”講，所以答案為“A”
3）insist作“堅決要求…該…；堅持認為…定要…”講時，其後賓語從句的謂語動詞用“(should)+動詞原形”
例如：I insisted that you (should) be there on time.我堅持認為你應該準時到那裡去。
4）insist 作“堅持（意見，看法）；堅持說，確信”講時，其後從句不用虛擬語氣。
例如：He suggested (that) he heard someone in the next room. 他堅持說他聽到隔壁屋子裡有人。
四、反意疑問句中的易錯點
1、在一般疑問句中，無論肯定的問或是否定的問，如果回答為肯定則用yes，反之則用no.特別注意如果出現省略則看下文所暗示的意義。
1.—Are you a new comer?
—Yes, I came here only yesterday.
2.—Isn't Tom a good student?
—Yes, he is excellent.
3.—Don't you think the composition good?
—No, It can't be any worse.
注意：在②③句中，當回答的意思與問句相一致時，則用No，譯為“是的”，當回答的意思與問句相反時，則用Yes，譯為“不”
2、情態動詞must
1.I must leave now, mustn't I ?
2.He must be in the classroom, isn't ?（表推測）
3.He must have finished his homework, hasn't he ? （表現在的結果）
4.He must have finished his homework yesterday afternoon,didn't he? （表過去）
當句子中有表示猜測的情態動詞時，其反意疑問句的構成不能再用原句中的情態動詞，而應根據原句在去掉情態動詞的情況下的主謂關係來確定其反問形式。
五、非謂語動詞中的易錯點
非謂語與其邏輯主語（即動作的執行者或承受者）之間有三種關係，如為主謂關係，則用現在分詞或不定式的主動式；如為被動關係則用過去分詞、現在分詞的被動（強調動作正在進行）或不定式的被動式（動作將進行）；如既無主動也無被動關係則只能用狀語從句或獨立主格結構（即非謂語加上自己的邏輯主語）
Judging/considering/genrally speaking/supposing 指說話者的動作，故只用主動式。如：
Having been ill in bed for nearly a month , he had a hard time passing the exam.
解析：從這個句子可以看出，句詞的邏輯主語與句子的主語he一致，並且是主謂關係，所以用了現在的分詞作狀語，同時，分詞的動作明顯地發生在句子的謂語動詞動作之前，故採用了現代分詞的完成式。
In order to improve English , ________.
A. Jenny's father bought her a lot of tapes.
B. Jenny's father bought a lot of tapes for herself.
C. A lot of tapes were bought by Jenny.
D. A lot of tapes were bought by Jenny father.
解析：根據不定式短語我們可以推知，句子的邏輯主語應該是人而不是物，所以，應該排除CD，再就是應該是Jenny提高自己的英語，而不是她爸爸，故答案先B.
________,we decided to go out for a walk.
A. It is fine B. It fine
C. Being fine D.It being fine
解析：主句主語we與動詞短語be fine之間既無主動關係與無被動關係，所以要加上自己的邏輯主語It，由於不存在主、被動關係，故不能選C項，而應該選D 項。
________more attention, the trees could have grown better. A. Given B.To give C.Giving D. Having giving
解析：give與主句的主語之間是被動關係，故選A.如為主動關係則選C.
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