[問題]白勇語法第三章Q19

[oneseven]

The peaks of a mountain range, acting like rocks in a streambed, produce ripples in the air flowing over them; the resulting folw pattern, with crests and troughs that remain stationary although the air that forms them is moving rapidly, are known as "standing waves."

(C) crests and troughs that stationary although the air that forms them is movig rapidly, is

(E) stationary crests and troughs although they are formed by rapidly moving air, is

Answer: C 請問如何排除答案

[dibert8]

題目有錯.
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