若从句来源于一个陈述句,那么,连词用that,在口语中that可以省略; 若从句来源于一个一般疑问句,连词则用if 或whether;
若从句来源于一个特殊疑问句,则连词就是疑问词(如what,who,where,when等) 例如:They believe that the computer will finally take the place of human beings.
(他们相信计算机终将代替人类。) (从句本来就是陈述句)
I wonder whether I should say something for him to the headmaster.
(从句来源于一般问句Shall I say something for him to the headmaster?)
He asked me where he could get such medicine. (他问我在哪儿能搞到那样的药。)