El Niño, the periodic abnormal warming of the sea surface off Peru, a phenomenon in which changes in the ocean and atmosphere combine allowing the warm water that has accumulated in the western Pacific to flow back to the east.
A. a phenomenon in which changes in the ocean and atmosphere combine allowing the warm water that has accumulated
B. a phenomenon where changes in the ocean and atmosphere are combining to allow the warm water that is accumulating
C. a phenomenon in which ocean and atmosphere changes combine and which allows the warm water that is accumulated
D. is a phenomenon in which changes in the ocean and atmosphere combine to allow the warm water that has accumulated
E. is a phenomenon where ocean and atmosphere changes are combining and allow the warm water accumulating
In-depth Explanation and Correct Answer Below (so you don’t see it while reviewing the question)
El Niño, the periodic abnormal warming of the sea surface… Explanation
El Niño, the periodic abnormal warming of the sea surface off Peru, a phenomenon in which changes in the ocean and atmosphere combine allowing the warm water that has accumulated in the western Pacific to flow back to the east.
(A) a phenomenon in which changes in the ocean and atmosphere combine allowing the warm water that has accumulated
There’s no main verb. This isn’t a complete sentence. Take out the modifier in the middle and this is easier to see. The second bit is also a modifier. So doesn’t make for a complete sentence.
El Niño, a phenomenon in which changes in the ocean and atmosphere combine allowing the warm water that has accumulated in the western Pacific to flow back to the east.
(B) a phenomenon where changes in the ocean and atmosphere are combining to allow the warm water that is accumulating
Missing a main verb. Take out the modifier, “the periodic…”, and it becomes clear that this isn’t a complete sentence. Also, use “where” for places. A phenomenon is not a place. Use “which” instead.
(C) a phenomenon in which ocean and atmosphere changes combine and which allows the warm water that is accumulated
This one is trying to draw you into parallelism/list that you don’t want with “which” and “which”. It is the changes that allow warm water that is accumulated to flow back. These aren’t two separate ideas. Also, there’s no main verb. Again, take out the modifier, “the periodic…”, and it becomes clear that this isn’t a complete sentence.
(D) is a phenomenon in which changes in the ocean and atmosphere combine to allow the warm water that has accumulated
Adding “is” makes this one a complete sentence.
(E) is a phenomenon where ocean and atmosphere changes are combining and allow the warm water accumulating
Use “where” for places. Usually physical locations. A phenomenon is not a place. Use “which” instead.
Correct Answer: D
For some SC guidance, here’s a link to a breakdown of GMAT sentence correction.