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# Two decades after the Emareld River Dam was built, none of

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Two decades after the Emareld River Dam was built, none of [#permalink]

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02 Nov 2004, 12:39
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Two decades after the Emareld River Dam was built, none of the eight fish species native to the Emareld 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 hypothesixed that sharply rising water temperature must be invloved in signaling the native species to begin the reproductive cycle.

Which of the following statements, if true, would most strengthen the scientist's hypothesis?

A. The native fish species were still able to reproduce only in the side streams of the river below the dam where the annual temperature range remains approximately 50 degrees.

B. Before the dam was built, the Emareld 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 Emareld River before the dam was built was 34 degrees whereas the lowest recorded temperature of the river after the damn was built has been 43 degrees.

D. Nonnative species of fish introduced into the Emareld 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 Emareld River are not native to any other river in North America.
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Last edited by ruhi on 02 Nov 2004, 14:09, edited 1 time in total.
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02 Nov 2004, 14:03
I will go w/ A.

A, A provides sort of the "control" group
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03 Nov 2004, 11:53
could you please explain why is it A??

OA is A, but i couldnt understand clearly.
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03 Nov 2004, 12:57
let me try to explain.... i am not very good at explaining...

The argument stated that the inadequate reprouctive cycle is caused by the change in water temperature (decrease). However, there could be other reasons that might cause the inadequate reproductive cycle. Choice A actually proves that temperature is the cause because the same fish species that live in where the temperature remains unchanged are able to reproduce.

Choice A strenghten the hypothesis because with everything else being equal, temperature would be the cause of the abnormal reproductive cycle.

Hope this helps....
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03 Nov 2004, 13:21
A reinforces the statement that adequate reproduction is possible even in the same river where the temperature is 50 degrees
03 Nov 2004, 13:21
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