The peaks of a mountain range, acting like rocks in a streambed, produce ripples in the air flowing over them; the resulting flow pattern, with crests and troughs that remain stationary although the air that forms them is moving rapidly, are known as “standing waves.”
B crests and troughs that remain stationary although they are formed by rapidly moving air, are
C crests and troughs that remain stationary although the air that forms them is moving rapidly, is
D stationary crests and troughs although the air that forms them is moving rapidly, are
E stationary crests and troughs although they are formed by rapidly moving air, is
E为什么不对呢，看这也可以阿
忘记贴正确答案了，答案是c
但是正确答案中也是有个although从句
看到解释了：
从句子的结构上讲就是WITH+名词（CRESTS AND TROUGHS）而后面是THAT引到的是一个定语从句，修饰CRESTS AND TROUGHS，而在这个从句中又有一个 用ALTHOUGH连接的转折分句。
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