whether 和 if 均可用来引导宾语从句，表示“是否”，如：don't know whether/if I will be able to come.我不知道我是否能来.She asked me whether/if I was interested in working for her. 她问我是否 有兴趣为她工作但也有差别：1、 whether 可以与 or 或 or not 连用，而 if 不可以，如：H e wondered whether he should wait or go .H don’t know whether he will come. or not2 介词之后用 whether , 不用 if .It depends on whether you will agree .3 不定式前面用 whether 不用 if .I wonder whether to stay here .5 当从句或主句放于句首时，用 whether ，不用 if .Whether this is true or not , I can't say .Whether I'll have time to go with you I am not sure6 引导表语从句用 whether ， 不用 if .The problem is whether we should go home or not8 作 discuss 的宾语，用 whether ， 不用 if .They are discussing whether they should open the door9、当表示“如果”时用 if,而不用 whether强化练习：1. The question has not been answered ____ Taiwan will be included on the Olympic torch relay route.A．that B ．whether C．which D．if2. You have not yet answered my question _____ I can join in the party tonight or not.A. whetherB. ifC. that D. which3．— 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. whether4．---What are you anxious about?---___________A. If we succeed B.That we can succeed C. Do we succeed D.Whether we can succeed5. Only when _____ the painting _____ decide ______the painting is worth buying.A. he sees, he can ,whether B. does he see, can he, ifC. he sees, can he ,whether D. sees he, he can,that6. _____ English is his favourite subjectA. I asked him if B. I asked him that whether C. I asked him that D. I asked him which7. _____ they’ll go to the Summer Palace ____ the weather.A. If; depends on B. Whether; depends upon C. Whether; depended on D. If; depended upon8.It isn’t quite _____ ______ he will be present at the meeting.A. sure; whether B. sure; if C. certain; whether D. certain; that9. _____ the 2008 Olympic will be held in Beijing is not known yet.A. Whether B. If C. Whenever D. That10. No one was sure _____ he would be asked to speak next year.A. when B. whether C. what D. how11. It is still a question to us all _____ there is any living thing in some other places in the space.A. whether B. which C. what D. where12. I doubt _____ he will come here on time.A. that B. whether C. when D. where13. The point is not who said the words, _____ they are true or not. A. but whether B. and whether C. but how D. and how13. “What did he ask you?” “_____ I would be late.”A. That B. When C. Where D. Whether15. He treated all the people around him,______he knew or he didn't know,______.A. if, friendly B. whether, friendlyC. if, in a friendly way D. whether, in a friendly way16. At the meeting, we discussed _____ we should employ more workers.A. if B. whether C. that D. 不填Answers: BADDC ABCAB ABADD B。