GMAT Practice Question Set #29 (Question 85-87)

Critical Reasoning Question #85: Biomass Decomposition  
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Methanogenesis describes the formation of methane by microbes known as methanogens. The production of methane is often the final step in the decomposition of biomass, such as that found in cow manure. Clearly, therefore, by taking the resulting increase in methane levels in the atmosphere over the past decade and then determining how many decades of such increases it would have taken the atmosphere to reach current methane levels from a hypothetical initial methane-free state, the maximum age of the Earth's atmosphere can be accurately estimated.

Which of the following is an assumption on which the argument depends?

(A)

The quantities of methane release into the atmosphere have not been unusually large during the past decade.

(B)

At any given time, all layers of the atmosphere have about the same methane levels.

(C)

There is methane that is released into the atmosphere from human activity, such as fossil fuel burning.

(D)

There is no method superior to that based on methane levels for estimating the maximum age of the Earth’s atmosphere.

(E)

None of the methane released into the Earth’s atmosphere is used up by plant activity.

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