英语中,“虽然”和“但是”不能在一句话里同时出现。"因为"和"所以"也不能在一个句子中同时出现。 although they are poor, they are friendly. 他们虽穷却友善。但不能是“although they are poor, but they are friendly.” because he didn't study hard, he failed in college. 但不能是“because he didn't study hard, so he failed in college.”