Dec 09 LR section 2 # 25 (question about sun)

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risktaker
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Dec 09 LR section 2 # 25 (question about sun)

Postby risktaker » Thu Feb 04, 2010 10:32 pm

Why the heck is B right? I thought the stimulus says greenhouses gases would be higher in atmosphere then than now. Doesn't B support this by showing this to be true? Why does it weaken the answer then? Thanks in advance guys.

Cambridge LSAT
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Re: Dec 09 LR section 2 # 25 (question about sun)

Postby Cambridge LSAT » Thu Feb 04, 2010 11:28 pm

final premise: liquid oceans (3 billion years ago) --> higher level of greenhouse gases (3 billion years ago)
conclusion: CO2 (3 billion years ago) > CO2 (today)

We know that the total level of greenhouse gases must have been higher than it is today, but was the level of CO2 higher than it is today? The conclusion assumes that what was true of the whole was likely true of one of the parts. Choice B weakens the conclusion because a higher level of methane in the atmosphere could have contributed to the overall level to such a degree that the level of CO2 was the same or lower than it is today.

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risktaker
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Re: Dec 09 LR section 2 # 25 (question about sun)

Postby risktaker » Fri Feb 05, 2010 8:45 pm

Wow, I did not see that at all. Thanks.




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