I don't know _________ he can find out the information

2个回答

  • if

    我不知道他是否能找到资料?

    语句通顺!

    如果是按你所说的那样的话,那么都可以选择!

    这是我从别处找来的一段帮助!

    whether与if的比较:

    一、whether和if都可以用作连词,引导一个名词性从句,表示“是否”.whether可以引导主语从句、表语从句、宾语从句和同位语从句;而if只能引导宾语从句.

    1.引导宾语从句既可以用whether,也可以用if,两者常可以互换.whether从正反两个方面提出疑问,选择意义较强,多用于正式文体中;而if多用于口语,比较强调单方面,如:

    He asked me whether / if I could lend him my bike.

    Could you tell us whether / if it snows in winter in Australia?

    I want to know whether / if you can come or not.

    She asked them whether / if they had gone there by car or by train.

    值得注意的是:

    ① whether 和if都可以和or not连用,但是whether之后可以直接跟or not,而if则不能,如:

    I don’t care whether or not your car breaks down.

    I don’t know whether or not he’s coming.

    但是不可以说:

    I don’t care if or not your car breaks down.

    ② whether引导的从句一般不可以为否定结构(选择问句的后一部分除外);而if则可以跟否定结构,如:

    I don’t care if she doesn’t come.

    I don’t care if it doesn’t rain.

    但是,在某些动词或形容词之后,则可以用whether引导一个否定结构的句子,这种结构往往表示肯定的含义,如:

    I wonder whether he doesn’t think too much of himself.

    其意思相当于:I think he does think too much of himself.

    ③ 在个别动词之后,如discuss 等,只跟用whether引导的宾语从句,如:

    They discussed whether they should close the shop.

    We discussed whether Mary could join us.

    ④ whether 可以引导从句作介词的宾语,而if则不能,如:

    I’m not interested in whether they’ll go or not.

    It depends on whether we have got enough money.

    ⑤ whether可以直接跟动词不定式连用,而if则不能,如:

    I didn’t know whether to laugh or to cry.

    She hasn’t decided whether to go or not.

    He was wondering whether to go home or stay at school.

    2.引导主语从句(包括从句在句首的位置)应当用whether,不用if,如:

    Whether it is true remains a problem.

    Whether he can stay with us is another matter.

    Whether he will come,I am not sure.

    Whether or not he did it,I cannot tell.

    3.引导表语从句用whether,不用if,如:

    The question is whether you should accept it.

    The question is whether he will speak at the meeting.

    4.引导同位语从句用whether,不用if,如:

    The question whether he’ll attend the meeting is essential.

    I am in doubt whether I should agree to the plan.

    二、whether 还可以引导让步状语从句,意为“不管;无论”;而if则不能引导这种从句,如:

    I shall tell her about it whether you agree or not.

    Whether or not the figures are accurate,we have to recheck them.

    Whether or not we had a baby,we could not survive just on my salary.

    三、if还可以引导条件状语从句,意为“如果;假如”,而whether则不能引导这种从句,如:

    We shall do this experiment if we have time.

    四、如果在从句中使用if表示“是否”容易与表示条件的状语从句混淆时,应注意避免使用if,例如:Please let us know if they are coming.这句话可以理解为“如果他们要来,请通知我们一下.”也可以理解为“请告诉我们,他们是否要来.”若表示后一层意思,应当使用,以免引起误会.