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19 Jan 2020, 05:39
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C
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
25%
(medium)
Question Stats:
79% (01:44) correct
21%
(02:03)
wrong
based on 1013
sessions
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Not Attempted Yet
Nuclear fusion is a process whereby the nuclei of atoms are joined, or “fused,” and in which energy is released. One of the by-products of fusion is helium-4 gas. A recent fusion experiment was conducted using “heavy” water contained in a sealed flask. The flask was, in turn, contained in an air-filled chamber designed to eliminate extraneous vibration. After the experiment, a measurable amount of helium-4 gas was found in the air of the chamber. The experimenters cited this evidence in support of their conclusion that fusion had been achieved.
Which one of the following, if true, would cast doubt on the experimenters’ conclusion?
(A) Helium-4 was not the only gas found in the experiment chamber.
(B) When fusion is achieved, it normally produces several by-products, including tritium and gamma rays.
(C) The amount of helium-4 found in the chamber’s air did not exceed the amount of helium-4 that is found in ordinary air.
(D) Helium-4 gas rapidly breaks down, forming ordinary helium gas after a few hours.
(E) Nuclear fusion reactions are characterized by the release of large amounts of heat.
Which one of the following, if true, would cast doubt on the experimenters’ conclusion?
(A) Helium-4 was not the only gas found in the experiment chamber.
(B) When fusion is achieved, it normally produces several by-products, including tritium and gamma rays.
(C) The amount of helium-4 found in the chamber’s air did not exceed the amount of helium-4 that is found in ordinary air.
(D) Helium-4 gas rapidly breaks down, forming ordinary helium gas after a few hours.
(E) Nuclear fusion reactions are characterized by the release of large amounts of heat.
12 Apr 2021, 02:30
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Bunuel
OFFICIAL EXPLANATION
This question asks us to weaken the argument. Recall: To weaken an argument, we typically must attack a premise—either expressed or suppressed—of the argument. Now the underlying premise of any controlled experiment is that there are no outside variables affecting its outcome. Two variables that come immediately to mind are 1) there may be another source for the helium-4, and 2) helium-4 may be naturally occurring in air. Now if the amount of helium-4 in the air after the experiment is the same as before the experiment, then clearly the researchers’ claim would be spurious. Hence the answer is (C).
General Discussion
24 Jan 2020, 07:06
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Bunuel
One line summary of the Argument:
Presence of measurable amount of He4 gas -----> Successful fusion
The obvious flaw here is that, it doesn't talk about the amount of the gas released.
A. This is irrelevant to the argument. Even if other gases were found in the chamber, it cannot give an indication whether fusion was attained. (Unless more details were provided)
B. Whether tritium and gamma rays were produced as byproducts or not, does not affect the argument.
C. If the amount of He4 gas did not exceed the amount of He4 gas found in ordinary air, it means that no new He4 gas was produced ie.. fusion did not occur. So C is the answer.
D. This could have been a potential answer if time was a factor under consideration, but since this is not a part of the argument, this answer can be eliminated.
E. This is also irrelevant to the conclusion.
