Self-study
Shortly after the Persian Gulf War, investigators reported that the area, which had been subjected to hundreds of smoky oil fires and deliberate oil spills when regular oil production slowed down during the war, displayed less oil contamination than they had witnessed in prewar surveys of the same area. ████ ████ ████████ ████ ███ ██████ ██ ██████████ ████████ ████████████ █████████████ ██ █ ██████ ██ ██████████ ████████ ██████ ████ ███ █████ ███████ ██████ ███ ██████████ ████ ██████████ ████ ██████████ ██ █████ ████████ ██ ███ █████████ █████████████ █████ ██ ███ ██████ ████
Structure: Description of Phenomenon
The stimulus describes a phenomenon: the postwar level of oil-related pollution in the area affected by the Persian Gulf War. Investigators point out that the area showed less oil contamination after the war than before the war, despite many oil fires and spills. They also point out that levels of a certain chemical — PAHs — were fairly low and comparable to levels in a different oil-producing area presumably not affected by the war.
Potential Resolutions
With Resolve, Reconcile, Explain-type questions, it's always important to ask what the tension is that we're trying to resolve. In this case, the "surprise" in the stimulus involves on two comparisons: comparing the Persian Gulf area after the war to how it was before the war, as well as to another area outside the war zone. The surprising phenomenon is that, even though there were many oil fires and spills, etc., the area displayed relatively low levels of PAHs, comparable to the Baltic Sea region, and less oil contamination than the same area before the war.
One way to resolve this tension would be to suggest that the thing we are comparing this situation to — "regular" oil production, whether in the Persian Gulf or in the Baltic Sea — actually produces more pollution than we might expect, so much so that all the fires and spills from the war still led to less contamination than pre-war oil production did. In other words, we could resolve the tension in this stimulus by suggesting that "regular" or even "relatively low" levels of PAHs and oil contamination from normal oil production might still be quite high.
22.
Which one of the following, ██ █████ ████ ████ ██ ███████ ███ ████████ ███████████ ██ ███ ███████████ ██████
a
Oil contaminants have ███████ █████████████ ███████ ██ █████████ ███████ ████ ██ ██████ ████████
This isn't helpful. This only applies to the comparison with the Baltic Sea region, and doesn't even help explain the tension embedded in that comparison. Notice that the stimulus doesn't compare the postwar Persian Gulf and the Baltic Sea with respect to "oil contaminants" in general, only with regard to PAHs. Oil contamination is mentioned in the comparison between prewar and postwar Persian Gulf contamination levels, which this answer choice doesn't help explain.
b
Oil contamination and ███ █████████ █████████ ████ ███████ ██ █████████ ███████ ████ ██ ██████ ████████
Like (A), this answer choice is only relevant to the comparison between the Baltic Sea region and the postwar Persian Gulf. It doesn't help explain why oil contamination is lower in the Persian Gulf area after the war than before.
c
Oil contamination and ███ █████████ █████████ ████ ███████ ██ ██████ ███████ ████ ██ █████████ ████████
You might think this answer choice resolves both comparisons in the stimulus. It certainly helps explain why the PAH levels in the Gulf area might be comparable to those in the Baltic Sea region: perhaps those levels were higher to begin with, but they dissipated fast enough by the time they were measured to be comparable to the levels from the Baltic Sea.
But this answer choice still doesn't help explain why oil contamination was lower in the Persian Gulf after the war compared to before, despite the "hundreds of smoky oil fires and deliberate oil spills" from the war. The region is the same in this comparison, so we can't explain the difference in contamination levels by appealing to a difference in climate.
d
Peacetime oil production ███ █████████ ██ ███ ███████ ████ ██████ ██ ████ ██████ ██ ████ ███ ███████ ███ ████████
This is correct. If peacetime oil production was highly polluting and involved "massive oil dumping", this helps explain how even the "hundreds of smoky oil fires and deliberate oil spills" from the war might not have caused as much contamination as peacetime oil production before the war.
You might think this answer choice fails because it focuses only on one comparison: it doesn't address the comparison to PAH levels in the Baltic Sea area. But though that is a comparison included in the stimulus, in a way it's less "surprising" than the comparison of the oil contamination levels in the Persian Gulf before and after the war. Without knowing about the war, there's nothing necessarily surprising about the Persian Gulf's PAH levels being about the same as another oil-producing region's. And knowing that levels of PAHs in the Persian Gulf area before the war were already "high" makes it possible to understand why it's surprising that they were "relatively low," similar to the Baltic Sea region, after the war.
So another way to think about this is that the comparison between the prewar and postwar Persian Gulf is actually the key comparison here. Without that comparison, there's not really a reason to compare the postwar Persian Gulf to the Baltic Sea. And having more details about prewar PAH and oil contamination levels in the Persian Gulf helps reconcile the main tensions in the stimulus.
e
The Persian Gulf ███ █████ ██████ ███ ███ █████ ███ ██████ ██████ ██ ████ ██████ ██ ██████████ █████████
This isn't relevant. We don't know how much damage was "originally expected." Even if "damage" refers to pollution here, the point of the stimulus is the implicit contrast between the pollution that existed before the war and the pollution actually caused by the war, not the pollution that was "expected" beforehand.