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Source: Official Guide for GMAT Review 2016 Critical Reasoning; #2


Which of the following, if true, would most

Which of the following, if true, would most strengthen the astronomer’s argument?

1 Explanation


John Robertson

o Question: What answer choice strengthens the astronomer's argument?

o His Argument: Stars w/ same chemical composition come from the same cloud of gas

o His supporting information: stars form from the same cloud of gas, each cloud has
unique chemical composition .

o Task: find an answer that most strengthens his argument of stars- same chem comp/same cloud of gas, simple english: find additional supporting information to what he already gave

o A: WRONG. Doesn't really address the same chem/same cloud argument. It talks about groups of stars, but that is sort of a level up from his conclusion GROUPS -> CLOUDS -> STARS. His thesis is about stars from clouds, the question is about stars from groups. So neither here nor there I think

o B: WRONG. Talks about how clouds with similar chem comps may be remote. The remoteness has nothing to do with chem comp, and it didn't even address the stars-> clouds connection, so I marked this wrong. Also, if this was true, it weakens his argument if there are clouds with same chem comp floating around.

o C: CORRECT. Directly addresses the cloud->star connection about how stars get the same chemical composition of their clouds. Who knows if his argument is wrong, but this strengthens his argument.

o D: WRONG: Talks about how stars from different parts of the universe have similar chem comps. This may be right, but it doesn't strengthen his argument, which you've been asked to do. Also, probably this is trying to make you make the false leap of reasoning that stars in different parts of the universe=different parent clouds. No way to know if this is true, GMAT just trying to be tricky here I think. Clouds could span huge parts of the universe.

o E: WRONG: This weakens his argument, which you've not been tasked to do. If astronomers can only sometimes determine the chem comps of stars an clouds, then that accuracy of determination is called into question, so how could the astronomer even have the conclusion that he made without being able to determine the chem comps. That would be his step one.

Dec 18, 2016 • Comment

Sam Kinsman

Good job, John - your reasoning is correct, and you got the right answer! :)

Dec 19, 2016 • Reply

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Section 8.4 Critical Reasoning

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