OG11-90,请教

90. 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."

(A)            crests and troughs that remain stationary although the air that forms them is moving rapidly, are

(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

Agreement

The subject of the second independent clause is the resulting flow pattern; this singular subject requires the singular verb is known, not the plural verb are known. While the long descriptive construction between the subject and verb may make it difficult to see this relationship, notice that the modifying phrase is set off with commas. The use of the active voice in the verbs of the subordinate clauses provides greater clarity of meaning.

这道题我选择的是E.    ABD是可以直接排除的.当答案是C. 请看og给的解释是E       The clause following although is awkward and unclear...

我真有点不明白 ,其实从语言简洁角度来说,E明显要比C要好........

恳求大家的指点!!

谢谢

although 中用了被动所以awkard

 E后面连接的是句子啊!!

难道,although 后一般连接是active voice?

要忠实原文。原文的意思是c和t保持稳定。而E的意思变成了稳定的c和t。原文意思是空气流动迅速，而E却变成了迅速流动的空气