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 know
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 know
The correct option is B (A) crests and troughs that remain stationary although the air that forms them is moving rapidly, 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, and C can, therefore, be eliminated because they use an incorrect plural verb form, are. Choice D 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. B, the best choice, uses the correct verb form, is, and correctly puts the although clause inside the predicate of the relative clause (that... rapidly).
(A) crests and troughs that remain stationary although the air that forms them is moving rapidly, 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, and C can, therefore, be eliminated because they use an incorrect plural verb form, are. Choice D 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. B, the best choice, uses the correct verb form, is, and correctly puts the although clause inside the predicate of the relative clause (that... rapidly).
