OG10-205解释有疑问

205.
   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

The main challenge in this sentence is to observe the agreement of subject and verb (the resulting flow pattern... is known...) despite the distraction of a complex intervening structure containing several plural elements (with crests and troughs...). Choices A, B, and D can, therefore, be eliminated because they use an incorrect plural verb form, are. Choice E uses the correct verb form, is,
   but it incorrectly introduces a dependent adverbial although clause into a prepositional phrase (with crests...). Choice D also makes this error. Such dependent clauses can only occur in the predicates of full clauses. C, the best choice, uses the correct verb form, is, and correctly puts the although clause inside the predicate of the relative clause (that... rapidly).

1.CE如何区分？解释中的这两句话怎么理解？

but it incorrectly introduces a dependent adverbial although clause into a prepositional phrase (with crests...).

E:,with stationary crests and troughs although they are formed by rapidly moving air, 这是个由with结构引导的插入语, 前后由逗号分开, 所以在with结构中再加入一个although从句, 是不可以的

correctly puts the although clause inside the predicate of the relative clause (that... rapidly).

 C: with crests and troughs
                            [that remain stationary although the air that forms them is moving rapidly],

定从修饰crests and troughs, 定从中套一个从句

 C: with crests and troughs
                    [that remain stationary although the air that forms them is moving rapidly],

定从修饰crests and troughs, 定从中套一个从句

2.选择C是与关系从句的谓语(remain)有关系么，这是although从句的要求么？

 是与remain有关系, 注意remain + adj 不等于 be+adj, 所以如果原句中出现remain , 正确答案中多数要保持, 不可简单的以be动词代替.

这个不是althoug从句的要求

 是与remain有关系, 注意remain + adj 不等于 be+adj, 所以如果原句中出现remain , 正确答案中多数要保持, 不可简单的以be动词代替.

这个不是althoug从句的要求

3.另外如何分析
  ’,with crests and troughs that remain stationary although the air that forms them is moving rapidly,’ 这句话？although是在that clause中么?

同上

同上

请同学们帮助解答，谢谢；