英语四个关联词词组中的“虽然……但是，though, but”，“因为……所以,beacuse, so”等关联词不能连用，只能用其中的一个连词。

因为though, because是从属连词，引导复合句；but, so是并列连词，引导并列句。一个句子不可能既是并列句又是复合句，所以though, but不能连用，beacuse, so不能连用。使用例句：

1. Though he is young, he knows much knowledge.He isyoung, but he knows much knowledge.2.Because Mary was ill, she was absent from school.或者：Marywas ill, so she was absent from school.