英语中的“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。例句：

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