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谁知道宾语从句中,如何区别if和whether的用法?

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谁知道宾语从句中,如何区别if和whether的用法?
谁知道宾语从句中,如何区别if和whether的用法?
whether与if作“是否”讲,在用法上有相同之处,也有不同之处.
一、相同之处.
1.whether和if都能引导宾语从句,常置于see,ask,learn,tell,wonder,doubt,find out等动词之后.
如:He asked me whether/is I could help him. I want to know whether/if he lives there.
2.whether和if都可用it作形式主语从句中.如: it's uncertain whether/if he'll come this evening.
3.在be uncertain/doubtful之后,常用whether引导宾语从句,有时也可以用if,如: We are uncertain whether/if Mary will come.
二、不同之处.
1.whether可置于句首引导主语从句,而if不能.如: ___the 2000 Olympic Games will be in Beijing is not known yet. A.whether B.If C.Whether D.That 答案是C.
2.whether可用在介词之后,引导宾语从句,而If则不能.如: Success depends on whether we make evough effort.
3.whether可引导表语从句,if则不能.如: The puestion is whether it is not worthdoing.
4.在名词之后引导同位语从句时,用whether而不用if.如: The puestion whether the students answered correctly should be decided by the teacher.
5.whether后可接不定式,而if不能.如: Please tell us whether to go or stay here.