although引导让步状语从句重要程度： 难易程度：(2017北京) _ birds use their feathers for flight, some of their feathers are for other purposes.A. Once B. If C. Although D. Because【参考答案】C【拓展延伸】1. although较正式，语气强。还可用倒装。Although he was tired(=Tired although he was), he went on working. 尽管他很累，但是他继续工作。2. although引导的从句放在主句前后均可，有时还可放在句中。Although many difficulties are still ahead, we are determined to make greater achievements. 尽管在前面的道路上还有许多困难，但是，我们决心要取得更大的成就。He often helps me with my English although he is quite busy. 尽管他相当忙，但是还常常帮我学英语.3. 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。但二者只能留一个。【特别注意】although 的几不：1. although不能指假设的情况。2. although不能作并列连词。3. although不能作副词，放在句首或句尾。1. We had to wait half an hour _ we already booked a table. A. since B. although C. until D. before 2. _, he does get annoyed with her sometimes. A. Although much he likes her B. Much although he likes her C. As he likes her much D. Much as he likes her3. he thought he was helping us with the work, he was actually in the way.A. AlthoughB. UnlessC. BecauseD. When4. The concert was a great success there wasnt a single empty seat in the concert hall, _ it was very cold. A. because B. when C. unless D. although5. Although he tries to talk to my classmates, but I still find it hard to make friends with him.(单句改错) 5. 去掉but 【解析】Although和but不能在同一句中使用，故此处去掉but。【特别提醒】although和but，because和so，enter和into，return和back不能在同一句中连用。你知道怎么表达尽管吗？_