2009高考英語二輪單選知識點練析

1. ― Have you known each other for long?
   ― Not very long, ____ we started to work in the company.

   A. after               B. before              C. when            D. since

2. ― Did you enjoy yourself at the party?

  ―Sorry to say I didn’t. It was ____ a meeting than a party.

   A. much of             B. more like           C. less of         D. more or less

3. He is rather difficult to make friends with, but his friendship, ____, is more true than any other.
   
   A. once gained                     B. when to gain

   C. after is gained                 D. while gaining

4. The river, ____ are covered with trees, is very long.

   A. which banks                     B. of which banks
 
   C. whose the banks                 D. the banks of which

5. ____ it will do us harm or good remains to be seen.

   A. If              B. Whether             C. That           D. Where

6. We should do more such exercises in the future, I think, ____ we did yesterday.

   A. as              B. which             C. that            D. than

7. I am so glad that I have found the same modern computer ____ I am working on.

   A. which            B. as            C. that            D. where

8. ____ method you choose, so long as you finish the job on time.

   A. It isn’t a matter to me what

   B. What doesn’t matter is that

   C. It doesn’t matter to me which

   D. No matter which

9. It was quite a serious mistake, ____caused by carelessness.

   A. which I think was                 B. I think which was  

   C. which I think it was              D. I think which it was

10. The young man went into the cinema and after ___seemed half an hour he came out.

    A. that              B. it               C. what           D. which

11. One of the men held the view ____ the book said was right.

    A. what that          B. what          C. that             D. that what

12. Soon they got to the bank. ____stood a big pine tree.

    A. In front of which         B. There            C. Where            D. It

13. He was impolite to the Custom Officer, ____, of course, made things even worse.

    A. who              B. that             C. what           D. which

14. After living with his grandparents in the countryside for ten years, the boy returned to the big city ____ his parents worked.

    A. which            B. where           C. that             D. when

15. ____ much advice I gave him, he did exactly what he wanted to.

    A. How               B. Whatever          C. No matter           D. However

16. It is not I but Mr. Green who ____ in charge of the company.

    A. is                 B. am                C. are                D. was

17. The students are talking about the strange people and stories  ____  they met in the adventure.

    A. that               B. which              C. what              D. whom

18. The first thing ____ you should do is to learn all the new words by heart.

    A. what               B. that               C. which            D. who

19. Is this the very factory ____ he visited last month?

    A. which              B. that               C. where          D. in which

20. He went home for lunch ____ the clock struck twelve.

    A. while              B. immediately         C. right away          D. at once

21. ―  ____ makes her different from the other students?

    ― Honesty, I think.

    A. How is it that                   B. How is that
    
    C. What is it that                  D. What it is that

22. She won’t leave the TV set, ____ her husband is waiting for his supper.

    A. as though           B. even though          C. whether             D. whenever

23. It is the teacher ____ taught me when I was a child ____ I am going to visit.

    A. that; which            B. who; which          C. who; that         D. whom; that

24. It was in the school ____ he had studied ____ he began the important experiment.

    A. that; where                   B. in which; which

    C. where; that                   D. where; in which

25. ____ on Monday night that all this happened?

    A. Is it           B. It is          C. Was it          D. It was

26. Is there anything else ____ you want to get ready for the party this evening?

    A. which           B. that           C. who              D. what

27. I ____ see him yesterday.

    A. really          B. do             C. did              D. does

28. ____ come again.

    A. Do              B. Can            C. May             D. Did

29. ____ be careful when crossing the street!

    A. Must            B. Should         C. Ought to         D. Do

30. It was ____ the old worker came that we ____ the  experiment.

    A. until; didn’t begin              B. not until; began

    C. until; began                     D. not until; didn’t begin

31. It is I ____ singing in the garden.

    A. who are             B. who is            C. that am          D. that is

32. Hardly ____ into the country ____ it began to rain.

    A.  we had got; when                B. we got; than

    C.  had we got; when                D. did we get; than

33. Not a single word ____ last night.

    A. he said             B. said he        C. did he say          D. had he said

34. Little ____ about what others think.

    A. he cares                         B. he doesn’t care

    C. does he care                     D. doesn’t he care
  
35. Seldom ____ any mistakes during my past few years of working there.

    A. would I make           B. have I made        C. I did make          D. shall I make

36. He is a good student, and works very hard; ____.

    A. so it is with her               B. so does she

    C. so is she                          D. neither does she

37. Only when it is hungry ____ attack a human being.

    A. a lion will         B. did a lion         C. will a lion         D. do a lion

38. Look! ____.

    A. Here your teacher comes

    B. Comes here your teacher

    C. Your teacher come here

    D. Here comes your teacher

39. No sooner ____ to shine ____ it clouded over again.

    A. the sun had started; than

    B. had the sun started; than

    C. the sun started; when

    D. did the sun started; when

40. So loudly ____ that even people in the next room could hear him.

    A. did he speak          B. spoke he          C. he spoke         D. should he speak

41. Not only ____ the book, but also he remembered what he had read.

    A. he had read          B. had he read         C. he did read         D. did he read

42. ____ , they continued the work.

    A. As it was late                   B. It was late as

    C. It was as late                   D. Late as it was

43. ____ the bus until it has stopped.

    A. Not get off                      B. Don’t get off

    C. Didn’t  get off                  D. Get not off

44. ____ are the days when teachers were looked down upon.

    A. Gone           B. Go              C. To go          D. Going

45. ____ rich and strong!

    A. Our country may become

    B. May our country become

    C. Our country becomes

    D. Does our country become

46. In the open boat, the four men, ____ was a doctor, met with a storm at sea.

    A. one of which                    B. one of who

    C. one of whom                     D. one of them

47. This is an illness that can result in total blindness ____ left untreated.

    A. after          B. if            C. since         D. unless

48. Let me introduce myself to you all, ____ ?

    A. may you         B. will you         C. won’t  I       D. won’t you

49. The unsold goods he brought home are useless to me, ____?

    A. aren’t they         B. are they            C. did he          D. didn’t he

50. Nobody has the right to go there to have dinner free,____?

    A. hasn’t it          B. has it        C. haven’t they           D. have they
答案及解析：
1.D。since 是從屬連詞,引導時間狀語從句,常與現在完成時連用。題中答語為省略句,補全為:We haven’t known each other very long. We have known each other since we started to work in the company.
2.B。題意為“與其說是晚會,倒不如說是個會議”。more ...than意為“與其說……倒不如說……”。
3.A。once gained是狀語從句的省略, 相當于once it is gained。
4.D。名詞/代詞+of+whom/which可引導非限制性定語從句,表示部分與整體的關系。C項應為whose banks。
5.B。whether 引導主語從句位于句首時, 不可用if替換。
6.A。在such...as結構中,as常引導定語從句。題中I think是插入語。
7.B。在the same...as/that結構中,as和that常引導定語從句。如果前后指的是同一物,通常用that(如:I have found the same computer that I lost);反之,則常用as。
8.C。 matter作動詞時, 意為“要緊,有關系”, 常用于否定或疑問句中。no matter which引導讓步狀語從句,缺少主句,故D項錯誤。
9.A。which引導非限制性定語從句, I think是插入語。
10.C。what 引導名詞性從句作介詞after的賓語。
11.D。that引導同位語從句;what the book said是同位語從句中的主語。
12.B。
13.D。which引導非限制性定語從句,指代主句的整個情況。
14.B。
15.D。However much引導讓步狀語從句,相當于No matter how much,意為“無論我給他多少建議”。
16.A。此句是強調句型。強調句子的主語(由并列連詞not...but連接),謂語應遵循“就近一致”的原則,故用is。
17.A。先行詞既指人又指物,關系代詞只能用that不能用which。
18.B。先行詞被序數詞、形容詞的最高級及only, any, few,little, no, all, very,last等修飾時,關系代詞常用that不用which。
19.B。
20.B。immediately除了用作副詞之外,還可用作從屬連詞, 引導時間狀語從句,相當于as soon as。有類似用法的詞或短語還有: directly, the moment, the instance, the minute等。
21.C。本題為強調句型的特殊疑問句。答語補全是It is honesty that makes her different from the other students, I think.就honesty提問,就形成了以上句式。
22.B。even though 相當于even if ,引導讓步狀語從句, 意為“即使,縱然”,符合題意。
23.C。 who引導定語從句,when引導時間狀語從句, that為強調句型的引導詞。
24.C。這是一個強調地點狀語的強調句。
25.C。強調句型的一般疑問句。
26.B。先行詞為all, much, little, everything, anything, nothing,none, the one等不定代詞時,關系代詞常用that不用which。
27.C。強調句子的謂語,要在謂語動詞前加助動詞do,does,did,謂語動詞用原形。
28.A。為了加強祈使句的語氣,在動詞前加do,表示懇求。
29.D。加強祈使句的語氣,不管動詞是系動詞還是行為動詞,都在動詞前加do。
30.B。 本題句式結構為強調句型。強調until引導的時間狀語從句,要把not放于until之前。
31.C。強調主語(指人)時,引導詞可用that或who,謂語動詞必須與所強調的主語保持人稱和數的一致。
32.C。在hardly...when...和no sooner...than...句型中,hardly和no sooner位于句首時,主句要用倒裝語序,且謂語動詞常用過去完成時態。
33.C。否定副詞never, not, hardly, little, seldom, rarely, nowhere及含有否定含義的短語in no way, not until, in no case, at no time, by no means等位于句首時,句子常用倒裝語序。  
34.C。    
35.B。
36.A。表示后者與前者的情況相同時,常用“So+系動詞/助動詞/情態動詞+主語”。但如果句子結構中既出現了系動詞,又出現了行為動詞或者其他不同的形式時,通常用“So it is with sb./sth..或It is/was the same with sb./sth..”。
37.C。only修飾句子的狀語(副詞、介詞短語或狀語從句)且置于句首時,句子的主謂要部分倒裝。注意:only修飾句子的主語放在句首時,主謂無須倒裝。如:Only he knows about it.只有他知道此事。
38.D。在here,there或副詞away,back,down,in, out,over,up等作狀語位于句首,且謂語是come,go,rush,run等不及物動詞的句子中,主謂要全部倒裝。這種倒裝句的主語通常是名詞,但如果主語是人稱代詞,則不倒裝。如:Here he comes.      
39. B。
40.A。so...that...句型中,so+形容詞/副詞位于句首時,主句中的主謂語要部分倒裝。
41.B。not only...but also連接兩個并列分句,且not only位于句首時,其引起的分句中主謂要部分倒裝。
42.D。as引導讓步狀語從句,意為“盡管;雖然”,從句常用倒裝語序。這種倒裝是把作表語的名詞或形容詞、作狀語的副詞(much)及動詞原形提到句首。如果表語部分是名詞,提前時通常將冠詞去掉。如:Although he is a child,he knows a lot.可改寫為Child as he is,he knows a lot.注意:如名詞前有形容詞修飾時,冠詞常保留(A little child as he is,he knows a lot.)。
43.B。這也是― 個not... until句型,主句為祈使句。
44.A。表語位于句首且主語較長或結構較復雜的句子,主謂通常全部倒裝。題意為“教師被瞧不起的日子一去不復返了�！�
45.B。表示祝愿的句子常用倒裝形式。又如:Long live the great unity of the peoples of the world.
46.C。 one of whom引導非限制性定語從句。
47.B。if left untreated意為“假如不進行任何治療”。that can result in total blindness是定語從句修飾illness。
48.B。陳述部分若是Let me開頭的祈使句,其附加問句要用will you;陳述部分若是Let’s開頭的祈使句,其附加問句要用shall we。
49.A。陳述部分有含否定詞綴的詞時,其附加疑問部分仍用否定式。
50.D。當陳述部分的主語是no one,nobody,none,neither等否定詞時,其附加疑問部分應用肯定式,主語常用they。

51. I don’t believe everything goes well with you, ____?
    A. do they          B. does it          C. don’t they         D. doesn’t it

52. Mr Wang must go to Beijing to visit Mrs Brown today, ____ he?

    A.  mustn’t         B. may not          C. can’t          D. needn’t

53. Jack said Betty had always been interested in geography, ____ ?

    A. hadn’t Betty          B. hadn’t she         C. didn’t Jack          D. didn’t he

54. What you told me is really true, ____?

    A. isn’t it              B.  isn’t what        C. didn’t you         D.  wasn’t it

55. I won’t let you in ____ you show me the written permission of the manager.

    A. apart from            B. unless        C. except       D. but

56. Everyone wants to have a holiday, but you have no idea ____ tiresome it is to rest.

    A. how               B. what           C. whether          D. no matter how

57. I felt somewhat sad and was about to leave ____ something happened which drew my attention.

    A. unless            B. until           C. when              D. while

58. I decided to pay a visit to my former teacher as soon as I ____.

    A. finish what I did          

    B. finished what I did

    C. would finish what I was doing

    D. finished what I was doing

59. We see the lightning ____ it happens, but we hear the thunder later.

    A. the moment                     B. for the moment  
   
    C. at the moment                  D. in a moment

60. ____ that I’m feeling all right, my brain is also beginning to work much better.

    A. For           B. Now         C. Since          D. Despite

61. These two countries are similar ____ they both have a high snowfall during winter.

    A. to that                        B. besides that

    C. in that                        D. except that

62. My cousin keeps the photo ____he can see it every day, as it always reminds him of his college days in
Florida.

    A. which            B. where              C. whether           D. when

63. You can arrive in Guangzhou on time for the fashion show____you don’t mind taking the night train.

    A. provided         B. unless             C. though           D. until

64. Most people usually have less money at the end of the month than ____ at the beginning.

    A. which is             B. which was           C. they have             D. it is

65. Doctors have said that as many as 50 percent of patients don’t take medicine  ____ directed.

    A. like               B. so                 C. which               D. as

66. Mr Smith was so angry at all ____ Bill was doing ____ he walked out angrily.

    A. that; what           B. that; that         C. which; which         D. what; that

67. Girl ____, she is much naughtier than a boy.

    A. although she was                  B. though she is  

    C. though was she                    D. although was she

68. The girl got herself into a serious situation____she was likely to lose control over the motorbike.

    A. where               B. which              C. while              D. why

69. I think you ought to end it ____ it is too late, or you’ll kill yourself.

    A. even if         B. before         C. so that         D. once

70. They were surprised that a four-year-old boy should work out such a difficult problem ____ they themselves couldn’t.
     
    A. once          B. then               C. while           D. if

71. I was advised to arrange for insurance ____ I needed medical treatment.

    A. nevertheless          B. although            C. in case             D. so that

72. I haven’t found my watch yet; in fact, I’m not sure ____ I could have done with it.

    A. where               B. whether              C. what            D. how

73. ― ____ in this street?

    ― I think Mr. Black is the richest man.

    A. Whom do you think is the richest man 
    B. Who do you think is the richest man
  
    C. Do you think who is the richest man

    D. Do you think whom is the richest man

74. ____ puzzled the mother most was ____the son would never agree with her.

    A. What; why           B. That; how           C. Which; when         D. What; where

75. ____ computers are of great benefit to the development of science and technology.

    A. The fact is what                  B. That the fact is   
    
    C. What the fact is that             D. The fact is that

76. Word has come ____ some excellent students will go on a study trip to Chicago next month.

    A. that               B. what            C. when                D. whether

77. The players expected there  ____  more free time before coming back to the country from abroad.

    A. is               B. being               C. have been         D. to be

78. It is well known to us all  ____  China sent up a manned spaceship to outer space successfully last year.

    A. that             B. what                C. which            D. when

79. ____ he was fired by the company is ____ he didn’t work hard.

    A. What; because                  B. Why; because

    C. Why; that                      D. That; because

80. The man who was being followed stopped from time to time ____ he wanted to tie his shoelaces.

    A. as if               B. like              C. what            D. as

81. Living things are dying out quickly. Let’s ask ____ destroying them in the past years.

    A. what part people have been playing

    B. people have played in

    C. what part people have played in

    D. people have been playing what part

82.The teacher found ____ difficult to decide ____ he would take with him to attend the conference.

    A. it; whom           B. himself; who          C. this; whom          D. that; who

83. No matter how fast we worked, ____.

    A. we couldn’t catch up with them

    B. and we couldn’t catch up with them

    C. so we couldn’t catch up with them 
   
    D. but we couldn’t catch up with them

84. The reason why I gave in is ____ if I didn’t.

    A. because she would be disappointed 
    
    B. that she would be disappointed

    C. because she would have a disappointment

    D. for she would be disappointed

85. ― ____ can I deal with such a situation?

    ― Take ____ measure you think best.

    A. How; whichever                    B. What; whatever      

    C. How; whatever                     D. What; whichever

86. Villagers often say our village is no longer ____ it used to be.

    A. what             B. that           C. which          D. how

87. This is certainly the case, but ____ it is a mistake or not I don’t know.

    A. if              B. even though        C. whether       D. that

88. The workers were making so much noise in the workshop, and the boss hurriedly went to see ____.

    A. what the matter was             B. what was the wrong
  
    C. what wrong was                  D. what was the matter

89. I remember ____ the company only owned a small shop.

    A. when              B. how              C. whether          D. what

90. The changes in our chemistry lab will cost quite a lot, ____ they will save us money in the long run.

    A. or                B. since            C. for                D. but

91. ____has finished the task ahead of time will be rewarded, though we don’t know who it will be.

    A. Those who          B. Anyone           C. Whoever           D. Who

92. He expressed his hope  ____ he would visit China again the next year, and this was the very hope ____ he expressed as soon as he arrived in the country.

    A. that; that        B. which; which        C. that; which         D. which; that

93. I often think of the years  ____ I worked with the foreigners, ____ has had a great effect on my later life.

    A. that; which       B. when; which          C. which; that         D. when; who

94. In the forest we observed some trees ____the leaves were black with disease.

    A. where             B. of which             C. in which        D. whose

95. I don’t believe the reason ____ he has given for not coming to the lecture.

    A. why               B. that                  C. how                D. what

96. By using ears one can tell the direction ____ a sound comes.

    A. in which          B. from which            C. with which          D. through which

97. I don’t like such a person ____ often lies before your face.
    
    A. what                B. that                 C. as          D. which

98. We have to delay the party till next week, ____we will not have something important to do.

    A. when                B. which              C. at which         D  that

99. Every day the mother seems to be busy until 10 o’clock at night, ____the rest of the family have fallen asleep.

    A. that                B. by which time           C. on time             D. whose time

100. He was found to be a thief, ____ disappointed his wife.

     A. who               B. that                 C. which                  D. whom

答案及部分解析：

51.B。陳述部分為I believe/think/suppose+that從句時,附加疑問部分應與從句保持一致。   everything,nothing,this,that在句中作主語時,其附加疑問句的主語要用it,但陳述部分的主語若是anybody,anyone,everybody,someone時,其附加疑問部分的主語常用they。

52.D。陳述部分的must表示“需要,必要”時,附加問句部分的謂語要用needn’t。  

53. D。

54.A。當陳述部分的主語為名詞性從句時,附加問句部分的主語用it,謂語要和主句的謂語相一致。

55. B。

56.A。how引導同位語從句。

57.C。when在此為并列連詞,相當于and at that time,常譯為“就在這時”。     

58.D。     

59.A。

60.B。now that意為“既然、由于”。

61.C。in that意為“因為”。

62.B�？崭裰械倪B接詞引導的應是地點狀語從句,故用where。

63.A。根據句意,空格中缺少一個表示“如果”并能引導條件狀語從句的連接詞。provided作連詞,表示規定的條件,意為“如果”;unless意為“除非”; though意為“盡管”;until意為“直到” 。

64.C。than引導比較狀語從句,完整的從句為“than they have money at the beginning of the month ”。

65.D。句中 take medicine as directed 相當于take medicine as they are directed,as引導方式狀語從句。

66.B。第一空:先行詞為all,由 that引導定語從句;第二空:that 與前半句中的so呼應,引導結果狀語從句。

67.B。though引導讓步狀語從句時,有時從句可用倒裝語序,用法相當于as,即Girl though she is相當于Girl as she is。

68.A。題中where引導定語從句,相當于in which。

69.B。before引導時間狀語從句,本意是“在……之前”,在此題中譯為“以免”。

70.C。while是并列連詞,意為“而,卻”,前后有對比的意味。

71.C。A和B都有“雖然”的意思,與題意不符。in case意為“以防萬一”,符合題意。

72.C。do with常與what連用;deal with常與how連用。

73.B。題中do you think為插入語,疑問詞在句中作主語。

74.A。        

75.D。

76.A。that引導同位語從句,解釋說明主語word(消息)的內容。

77.D。there to be...相當于賓語從句(that)there would be...。

78.A。句中it作形式主語,真正的主語是由that 引導的從句。

79.C。why引導主語從句作主語時,表語從句不能用because引導,只能用連接詞that,且通常不可省略。

80.A。as if 意為“好像”。    

81.C。

82.A。第一空用形式賓語it,第二空可以用who或whom引導賓語從句并在從句中作take的賓語。

83.A。no matter how 引導讓步狀語從句,故只可選A,構成主從復合句。

84.B。主語是reason時,表語從句用that 引導。   

85.C。

86.A。what引導表語從句,且在從句中作表語。

87.C。引導賓語從句時,whether 和if常可互換,但如從句提前,則只能用whether。

88.D。what is/was the matter的語序在任何情況下都不變化,因為what在句中作主語。

89.A。when引導賓語從句。其他選項均不符題意(我記得這家公司過去僅有一家小商店的時候)。

90.D。根據題意,兩個分句間為轉折關系。in the long run意為“最終地”。

91.C。whoever相當于anybody who,A項主謂不一致。

92.A。第一空:that引導同位語從句。第二空:that引導定語從句。因為先行詞有the very 修飾,故不可用which。

93.B。根據句意,第一空需填關系副詞when; 第二空which引導非限制性定語從句,指代主句的整個情況。 
94.B。

95.B。根據句意,要填的關系代詞在定語從句中作given的賓語,故用that。

96.A。direction常與in連用。      

97.C。    

98.A。

99.B。根據從句的時態判斷,所填詞語必須含有“到……時候為止”的意思,并作從句的時間狀語。that不可引導非限制性定從句。on time意為“及時”,不符題意。D項錯誤,此題無所屬關系。

根據英語從句在句子中的句法作用，從句可分為三類：名詞性從句，形容詞性從句和副詞性從句。通過對引導從句的各種引導詞進行觀察，我們不難發現，有的從句可以直接從引導詞的形式和意義上來區分。如：Though the old man is over seventy, he still sees well and hears well. 我們一讀此句，就可以認定，由Though引導的從句是一個讓步狀語從句。因為though只能引導讓步狀語從句，不能引導其它從句，但是有些引導詞卻能引導多種從句。如引導詞when：既可以引導時間狀語從句又可以引導定語從句，還可以引導名詞性從句。此外，象that，where等，三類從句均可引導；who既可引導定語從句，又可引導名詞性從句；so that 即可引導目的狀語從句，又可引導結果狀語從句……因此，這些形同義不同的引導詞給我們理解、掌握、運用各種從句帶來了很大困難。另外，搞不清楚從句在句子中所起的作用，就不能正確理解原文。那么，怎樣正確區分各種形同義不同的引導詞引導的從句呢？ 

１、 分析句子結構以區雖從句的種類 
遇到一個復合句，首先要分析其句子結構，看從句在整個句子中起什么作用，那么它就是什么從句。 
２、 分析引導詞的句法作用以區別從句的種類 
that這個詞即是引導同位語從句，又可引導定語從句，這種兩種從句從形式和結構上看特別相似，如何區分呢？ 
區分that引導的是同位語從句還是定語從句的方法是，看that在從句中是否充當句子成分，若that在從句中不充當任何成分，則為同位語從句；若that在從句中充當主語或賓語，則為定語從句。 
３、 根據被修飾詞來判斷從句的種類
 定語從句常常修飾一些具有實際意義的名詞，如：the film；the student；the book；a house等等。而同位語從句常常修飾一些表示抽象概念的名詞，如fact、idea、promise、truth等，用來說明這些名詞所表示的具體內容。狀語從句在句子中常用來修飾謂語動詞。 
４、 根據從句前詞的詞性來判斷從句的種類 
賓語從句分兩種：動詞的賓語從句、介詞的賓語從句。賓語從句前肯定是動詞或介詞。定語從句是用來修飾名詞或代詞的，所以其前一定是一個名詞或代詞。 
５、 根據上下文意義和結構形式上區分從句的種類 
如so that即可引導目的狀語從句，又可引導結果狀語從句，如何區分呢？主要從以下兩點來區分。 
①根據上下文意義判斷�！耙员恪�…”表示目的，是目的狀語從句，“以致于……”，“結果……”表示結果，是結果狀語從句。 
②從結構形式上來分辨。so that前有逗號，為結果狀語從句，反之，則為目的狀語從句。有時，so that前無逗號，這里要看從句中有無can、could、may、might、will、would、should 等情態動詞，如果有，則多是目的狀語從句，若沒有，則多是結果狀語從句。