because 与 so、although 与 but 不能在同一句中同时使用，这是初中英语的经典考点。
要点讲解
- because 因为（原因状语从句）：He didn't come because he was ill. 他没来因为他病了。
- so 所以（结果）：He was ill, so he didn't come. 他病了，所以没来。
- because 与 so 不能同句使用：不能说 Because he was ill, so he didn't come.
- although/though 虽然（让步）：Although he is old, he works hard. 虽然他老了，但他工作努力。
- although 与 but 不能同句使用：不能说 Although he is old, but he works hard.
- unless 除非（= if...not）：You will fail unless you work hard. 除非你努力，否则你会失败。
- when/while/as 当……时候；before/after 在……之前/后；until 直到。
经典例句
- Although it was late, he went on working.
虽然很晚了，他仍继续工作。 - We didn't go out because it was raining.
因为下雨，我们没有出去。 - I'll call you as soon as I arrive.
我一到就给你打电话。
易错提醒
- 记住：because/so 二选一，although/but 二选一，不能成对出现在同一个句子中。