Many geologists theorize that the trail of volcanic craters and cinder

Experts help required. I am not sure if this question assumes that the test-takers know the workings of a certain phenomenon.

IMO you need volcanic/geologist technical knowledge to answer this question. Does the gmat official test allows this type of questions?

Many geologists theorize that the trail of volcanic craters and cinder cones along the Snake River plain of southern Idaho was produced as the North American continent slid westward over a stationary' "plume," a vertical channel through which molten rock rose intermittently from the Earth's core to burst through its crust.

Which of the following, if true, tends to support the geologists' theory of how the trail was produced?

(A) The largest craters and cinder cones are on the eastern margin of the trail.
(B) The most violent volcanic activity apparently occurred at the western margin of the trail.
(C) The craters and cinder cones are evenly spaced throughout the extent of the trail.
(D) The newest craters and cinder cones are on the eastern margin of the trail.
(E) The craters and cinder cones on the western margin of the trail generally took longer to form than did those on the eastern margin

Grammatically or with GMAT strategies/psychology its not possible to answer this one, at least not for me.
Tried my best to answer with highlighted modifiers that are extreme.
Not sure how each of them helps but A, B and C are not at all a possibility.
Between D and E, D looks similar to A, B and C logically but both are opposite to each other.

So, I went with language that is not extreme in sense and thus chose E.

Contrary to some requests here, this question does not require geological knowledge.
On the other hand, I was confused between A and D and chose A.
Can some expert tell me the basis for choosing D over A?

For this question, it helps to visualize the process of forming the trail of volcanic craters.

Imagine a continent sliding westwards over a single point (i.e. the stationary plume). Each time a crater or cone is formed, the continent moves further west, and a new crater or cone is formed to the east of the old one. Over time, this creates a trail of craters and cones that stretches from from west to east. Notice the oldest crater will be on the westernmost end of the trail. The newer craters will be on the eastern end.

Let's now consider the answer choices:

There is no reason that the continent moving westwards would create bigger cones on the eastern margin. Since this doesn't support the geologists' theory, we can eliminate (A).

If the continent moved westwards over a stationary plume, the newest craters would be on the eastern end of the trail. Since this supports the geologists' theory, it's correct.

I hope that helps!

Hi, I don't follow. Continent and new craters are formed in the West direction. New craters are formed to the West of old ones...
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­The CONTINENT is sliding westward. Since the plume is stationary, it "moves" eastward relative to the continent.

Picture the very first crater. When it was formed, it obviously aligned with the plume. But if the continent (along with the first crater) has drifted 1000 meters westward since then, the plume, and any new craters, will be 1000 meters to the EAST of the first crater. Newer craters are further to the east while older craters are further to the west.

If that's still tough to visualize, grab a sheet of paper and a pen or marker. Slide the paper to the left ("westward") while holding the pen steady on the paper to draw a line (or moving it up and down to make dots). The newest markings will be to the right (the "eastern" side of the trail).

I hope that helps!­