7. although; though; as 三者均可表示“尽管;虽然”,引导让步状语从句。although用法较正式,语气较强;though较常用;as则主要用于倒装句。它们的用法有如下几点值得注意: 状语从句由although, though或as引导,主句之前不可有but, and, ...