答案：A

题目分析：句意：虽然他是一个小男孩，但是他英语说的很好。 although较正式，语气强Although he was tired, he went on working； although引导的从句不能与but, however连用，但可与yet, still连用。不能说：Although he was old, but he worked hard. 应把but去掉。当然，保留but而去Although也可。故选A。