宾语从句引导词,一般是三种：
1、如果宾语从句不缺少任何成分,则引导词为that,不过that有时经常可以省略。
如：i dont know (that) he is a teacher.
2、如果宾语从句缺少“是否”的疑问词,则引导词为if/whether.不过用whether最好,有时候if是不能使用的。
如：i want to know if/whether you are good at english.
3、如果宾语从句缺少其他成分,则引导词为相应的可以补充句子完整的疑问词,一般分为疑问代词who/whom/what/which/whose或疑问副词when/where/why/how等。
如：can you tell me how i can get to the bus station?
i dont know who you are looking for.