宾语从句的连接词主要包括以下三类：1．连词that,只起连接作用,在从句中不作句子成分,也无词汇意义,在口语中常被省略. eg. He knew （that） he should work hard. 2．连词if 、whether,它们起连接作用,在从句中不作句子成分,作“是否”解,在口语中多用if. eg. Tom don't know if/whether his grandpa liked the present. He asked me whether or not I was coming. 一般情况下,if 和whether可以互换,但以下3种情况只能用whether： ①在不定式前：__________to go there or not hasn't been decided. ②在介词前：It depends on（依靠） ___________ it is going to rain. ③与or not连用：They are talking about _______________ to go there or not. 3．连接代词who, whom, whose, what, which,连接副词when, where, why, how, 它们起连接作用,作句子成分,各有自己的意义. eg. The teacher asked the new students which class he was in. I wonder where he got so much money.定语从句的连接词可以参见如下表格：
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