宾语从句中什么时候一定用weather,什么时候一定用if.

题目

宾语从句中什么时候一定用weather,什么时候一定用if.

答案

本来whether与 if在宾语从句中意思差不多,
I wonder if...=I wonder whether...
I see if...=I see whether...
I ask if...=I ask whether...
I try if...=I try whether...
I don't know if...=I don't know whether
1.但是当介词后的宾语从句,只能用whether,不能用if
It depends on whether you will agree.这取决于你是否同意.
2.在动词不定式前只能用whether,不能用if.
I wonder whether to stay here another week.
我想是否在这儿在呆一周.
3.用or表示选择概念时,用whether,不能用if.
He wondered whether he should wait for them or go on.
He wondered whether she liked it or not.
他不知道是等他们,还是继续往前走.
4引导表语从句只能用whether,不能用if.
The problem is whether we will go there by bus or by plane.
另外whether还可以引导主语从句,主语从句不用if