只能用if 引导的宾语从句 为什么if只能引导宾语从句和主语从句
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1\u3001if,\u53ef\u4ee5\u5f15\u5bfc\u3010\u5bbe\u8bed\u4ece\u53e5\u3011\uff0c\u610f\u601d\u662f\u3010\u662f\u5426\u3011\uff0c\u7ecf\u5e38\u548cwhether\u5bf9\u6bd4\uff0c\u4e00\u822c\u53ef\u4ee5\u4e92\u6362\u3002\u4f46\u6709\u4e00\u4e9b\u60c5\u51b5\u53ea\u80fd\u7528whether\uff1a
\u2460\u4f5c\u4ecb\u8bcd\u5bbe\u8bed\u65f6\uff1b\u2461\u4e0eor not\u8fde\u5728\u4e00\u8d77\u642d\u914d\u65f6\u3002
\u4f46\u662f\uff0c\u5728\u4e3b\u8bed\u4ece\u53e5\u3001\u8868\u8bed\u4ece\u53e5\u3001\u540c\u4f4d\u8bed\u4ece\u53e5\u4e2d\uff0c\u8868\u793a\u662f\u5426\uff0c\u90fd\u53ea\u80fd\u7528whether\uff0c\u800c\u4e0d\u7528if.
2\u3001if\u8fd8\u53ef\u4ee5\u5f15\u5bfc\u3010\u6761\u4ef6\u72b6\u8bed\u4ece\u53e5\u3011\uff0c\u610f\u601d\u662f\u3010\u5982\u679c\u3011\u3002
3\u3001if\u8fd8\u6709\u56fa\u5b9a\u77ed\u8bed\u642d\u914d\uff1a
if only \u8981\u662f\u3001\u3001\u3001\u3001\u3001\u3001\u8be5\u6709\u591a\u597d\uff0c\u5f15\u5bfc\u865a\u62df\u6761\u4ef6\u53e5\u3002
only if\u53ea\u8981\uff1b\u53ea\u6709\u5f53\u3001\u3001\u3001\u3001\u3001\u65f6\uff0c\u5f15\u5bfc\u6761\u4ef6\u72b6\u8bed\u4ece\u53e5\u3002
as if=as though,\u4f3c\u4e4e\uff1b\u597d\u50cf\uff0c\u5f15\u5bfc\u8868\u8bed\u4ece\u53e5\u6216\u865a\u62df\u6761\u4ef6\u53e5\u3002
even if=even though,\u5373\u4f7f\uff1b\u5c3d\u7ba1\uff0c\u5f15\u5bfc\u8ba9\u6b65\u72b6\u8bed\u4ece\u53e5\u3002
\u795d\u4f60\u5f00\u5fc3\u5982\u610f\uff01
I wonder if / whether I can get some advice from you.
Ask him whether / if he can come.
但在有些情况下，whether和if的用法有一定区别。
1. whether引导的从句常可以与连词or或or not直接连用，而if一般不能。如：
正： Let me know whether you can come or not.
误： Let me know if you can come or not.
2. 当宾语从句提到句首时，只能用whether引导，而不能用if。如：
正： Whether it is true or not, I can’t tell.
误： If it is true or not, I can’t tell.
3. whether可以引导带to的不定式，if则不能。如：
正： I don’t know whether to accept or refuse.
误： I don’t know if to accept or refuse.
4. whether及其引导的成分可放于介词之后，作介词的宾语，但if不能。如：
正： I worry about whether I hurt her feelings.
误： I worry about if I hurt her feelings.
5. whether可以引导从句，作主语、表语或同位语，而if不能。如：
正： It was uncertain whether he would come.
误： It was uncertain if he would come.
正： His first question was whether Tom had arrived yet.
误： His first question was if Tom had arrived yet.
正： We must consider the question whether we will take these measures.
误： We must consider the question if we will take these measures.
你是说if和whether的选择吗？ 如果是，那就只有一条：
宾语从句是否定时，常要用if，避免用whether（章振邦P.688、疑难集释p453）
I don’t care if it doesn’t rain.
I wonder if it doesn’t rain.
I wonder if it works.
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