noboru wrote:
Official Guide for GMAT Verbal Review, 2nd EditionPractice Question
Question No.: 35
Page: 129
Difficulty: Two decades after the Emerald River Dam was built, none of the eight fish species native to the Emerald River was still reproducing adequately in the river below the dam. Since the dam reduced the annual range of water temperature in the river below the dam from 50 degrees to 6 degrees, scientists have hypothesized that sharply rising water temperatures must be involved in signaling the native species to begin the reproductive cycle.
Which of the following statements, if true, would most strengthen the scientists’ hypothesis?
(A) The native fish species were still able to reproduce only in side streams of the river below the dam where the annual temperature range remains approximately 50 degrees.
(B) Before the dam was built, the Emerald River annually overflowed its banks, creating backwaters that were critical breeding areas for the native species of fish.
(C) The lowest recorded temperature of the Emerald River before the dam was built was 34 degrees, whereas the lowest recorded temperature of the river after the dam was built has been 43 degrees.
(D) Nonnative species of fish, introduced into the Emerald River after the dam was built, have begun competing with the declining native fish species for food and space.
(E) Five of the fish species native to the Emerald River are not native to any other river in North America.
Data:- Dam built (lets call it X) , Fish did not reproduce enough( Lets call it Y)
- Average annual temp decreased (Lets call it Z)
Notice that we have correlation implied between:
- X & Y
- Z & X
- Z & Y
Conclusion:- In order to signal (I assume that natures signals) -> the water temp is rising.
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Assumptions:- Nature signals to fish to reproduce by rising the water temp
- High enough temp -> fish reproduce
[V] - A - This indeed strengthen one of the assumptions.
[X] - B - This might explain why the overall fish population decreased, by telling us that an essential factor for breeding was not available, but it got nothing with conclusion (temperature is not mentioned).
[X] - C - This choice have no effect. In addition, a signal data point cannot indicate a general trend.
[X] - D - This might explain why the overall fish population decreased by telling us that critical factors for the fish survival was scarce, but it got nothing to do with the conclusion.
[X] - E - Clearly out of scope.