名词性从句中，这两项语法规则特别重要，是考试的重点与难点，必须掌握。
一、用whether不用if 的5种情况：
① 引导主语从句,表语从句,同位语从句时。
Whether there is life on the moon is an interesting question.
The question is whether we should help her.
② 作discuss的宾语时。
We'll discuss whether we should have a meeting.
③ 作介词宾语时。
Everything depends on whether we have enough money.
④ 从句后有"or not"时。
I wonder whether he will come or not.
⑤ 后接动词不定式时。 Can you tell me whether to go or to stay?
二、"坚决要命类动词"
下列表示"建议"、"命令"、"请求"的动词后面的宾语从句中要用虚拟语气，谓语用"should 动词原形"，should 可以省略：我把它们简称"坚决要命类动词：
一坚持：insist
二命令：command ，order
四建议：suggest，advise，propose, recommend
五要求：ask (beg ), desire, demand, require request
外加
三个词：prefer, urge, maintain 如：
I insist that she (should) do her work alone. The commander ordered that troops (should) set off at once.
One of the requirements for the experiment is that the material should be hated to its burning temperature。（should）
The teacher desired that all the exercises should be handed in Before school was over。
牛刀小试
1.We don't doubt____he can do a good job of it.
A. whether B. that C. what D. why
2.It depends on___we have enough time.
A. if B. if or not C. that D. whether
3.It isn't decided yet____we will attend the meeting.
A. if B. why C. that D. whether
4.Some researchers believe that there is no doubt ____ a cure for AIDS will be found.
A. which B. that C. what D. whether
5.We haven't settled the question of ______ it is necessary for him to study abroad.
A. if B. where C. whether D. that
6.We should consider the students' request ___the school library（should） provide more books on popular science.
A. that B. when C. which D. where
7.The limits of a person's intelligence, generally speaking, are fixed at birth,
but ________he reaches these limits will depend on his environment.
A. where B. whether C. that D. why
8.It doesn't matter _____ you pay by cash or credit card in this store.
A. how B. whether C. what D. why
9.Everyone in the village is very friendly. It doesn't matter ___ you have lived there for a short or a long time.
A. why B. how C. whether D. when
10.It doesn't matter __you turn right or left at the crossing—both roads lead to the park.
A.whether B. how C. if D. when
11.We will go swimming ---------- it is fine tomorrow．
A. While B. if C. when D. whether
12. You have not yet answered my question _____ I can join in the party tonight or not.
A. whether B. if C. that D. which
13.—I d like to invite you to a party this evening.
—Thank you, but _____ I'll be free I m not sure at the moment.
A.While B. If C. When D. Whether
14.---What are you anxious about? ---___________
A. If we succeed B.That we can succeed
C. Do we succeed D.Whether we can succeed
15.Only when _____ the painting _____ decide ______the painting is worth buying.
A. he sees, he can ,whether B. does he see, can he, if
C. he sees, can he ,whether D. sees he, he can,that
16. _____ English is his favourite subject
A. I asked him if B. I asked him that whether
C. I asked him that D. I asked him which
17. _____ they'll go to the Summer Palace ____ the weather.
A. If; depends on B. Whether; depends upon
C. Whether; depended on D. If; depended upon
18.It isn't quite _____ ______ he will be present at the meeting.
（it is ...that 结构中只能有certain不能用sure）
A. sure; whether B. sure; if
C. certain; whether D. certain; that
19. No one was sure _____ he would be asked to speak next year.
A. When B. whether C. what D. how
20. I doubt _____ he will come here on time.
A. That B. whether C. when D. where
21.Mike's father, as well as his mother, insisted that he____ home.
A. stayed B. could stayed C. has stayed D. stay
22.Our monitor requested that______.
A.all the class studied more carefully the problem.
B. the problem was more carefully studied.
C. with great care the problem could be studied
D. all the class study the problem more carefully
23.He insisted that he _____really very tired and that he ___to have a rest.
A.was, be allowed
B. was, must be allowed
C. should be, must be allowed
D. should be, be allowed
24.His suggestion that you _____once more sounds reasonable.
A. try B. tries C. must D. can try
25.We insisted that he ______ seriously ill and that a doctor ______ for at once.
A.should be; should be sent
B. was; be sent
C. were; should be sent
D. was; must be sent
26.My suggestion is that a few more people______ there to help me.
A. be sent B. have sent C. sent D. should sent
27.The teacher demanded that the exam____ before eleven.
A.must finish B. would be finished
C. be finished D. must be finished
28.I suggest that Mary ______to the lecture herself.
A. go B. goes C. would go D. went
29.He insisted that she____ the matter at the meeting.
A.take up B. takes up
C. will take up D. would take up
参考答案：
1-5: BDDBC 6-10: ABBCA 11-15: BADDC
16-20: ABDBB 21-25: DDAAB 26-29: ACAA
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