Temperatures in the Pacific Northwest have risen steadily

[A AAPL]

Princeton Review

Temperatures in the Pacific Northwest have risen steadily since 1981, averaging 2.07 degrees Fahrenheit warmer north of the 46th parallel than in the previous decade. Precipitation and water-table levels, which have historically maintained a measurable relationship to each other (within a scaled range of two to four points), have varied drastically from 1987 to 1991, sometimes deviating as much as six points in fewer than eight months. Reports from Canada indicate a similar median temperature increase, estimated at 2.02 degrees Fahrenheit; research from a 1992 study measures the relational swing in moisture levels at no more than three points.

Of the following, which conclusion is best supported by the evidence above?

A. The higher the temperature of a given area, the more likely it is that the water levels will vary.
B. The variation in temperature in the last decade has been less than the fluctuation of moisture.
C. When temperatures rise north of the 46th parallel, natural water exchange between land and atmosphere must change in the same proportion.
D. Within the last ten years, water table and precipitation levels have varied more in the Pacific Northwest than they have in Canada.
E. Canada will have more stability in weather than will the area of the United States above the 46th parallel.

OA D

[D deloitte247]

OPTION A - INCORRECT
This also seems like a good conclusion to the argument, but the rate at which the water level varies is different at the span of some years and location. So, the given information here is not detailed enough to serve as a conclusion to the argument.

OPTION B - INCORRECT
It is true that the variation of temperature has been lesser than the fluctuation of moisture but this given conclusion is stereotypical in nature.
It is only concerned about the rate of temperature to moisture, not the location and the years involved which makes it not best supported by the argument.

OPTION C - INCORRECT
This cannot serve as a conclusion to the argument because it is not the point to be proved with this argument. The argument isn't just about the rise in temperature in the 46th parallel but also in Canada which has similar reports

OPTION D - CORRECT
Within the last years which is between 1987 to 1991 as stated in the argument, the water table and precipitation levels have varied more in the pacific Northwest than they have in Canada. With adequate evidence in the argument that claims that the pacific Northwest precipitation can vary as much as six points unlike Canada which is no more than three points.

OPTION E - INCORRECT
The argument here is not about comparing locations with stable weather. So, this cannot serve as a conclusion to the argument.

[BTG Expert Team]

What we see: a Critical Reasoning conclusion question. The passage gives numbers for two places, and we pick the claim those numbers back up best.

Step 1. Sort the numbers by place and by kind.
What we see: Pacific Northwest, temperature up 2.07 degrees, and the precipitation to water-table relationship swung "as much as six points" from 1987 to 1991. Canada, temperature up about 2.02 degrees, and a 1992 study puts its moisture swing at "no more than three points."
What it means: the temperatures in the two places are almost the same. The moisture swings are not: up to six points in the Northwest against at most three in Canada.
What we do and why: the clear, backed-up fact is the moisture comparison. Look for the choice that says the Northwest's water levels varied more than Canada's.

Step 2. Check each choice.
A. "The higher the temperature, the more water levels vary." The two places warmed by almost the same amount, so the passage cannot show a link between more heat and more variation.
B. It compares degrees of temperature with points of moisture. Those are different units, so "less than" means nothing here.
C. "Must change in the same proportion." The passage gives no proportion at all.
D. Over the last ten years, the Northwest's water-table and precipitation levels varied more than Canada's. Six points against no more than three supports this directly. Keep.
E. A forecast about Canada's future weather. The passage only reports the past.

The trap: A. The passage opens with rising temperatures, so a rule linking heat to water levels sounds like its point. But with nearly equal warming in both places, the data cannot support it.
Faster way: when a passage gives the same kind of number for two places, the supported answer usually just compares them.
Takeaway: a conclusion question rewards the claim with the least stretch. A direct comparison of the numbers given beats any rule about cause.

Answer: D