GMAT Practice Question Set #46 (Question 136-138)

Critical Reasoning Question #138: Burning Methane  
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Proposal: Carbon dioxide and methane in the atmosphere block the escape of heat into space. So emission of these “greenhouse” gases contributes to global warming. In order to reduce global warming, emission of greenhouse gases needs to be reduced. Therefore, the methane now emitted from open landfills should instead be burned to produce electricity.

Objection: The burning of methane generates carbon dioxide that is released into the atmosphere.

Which of the following, if true, most adequately counters the objection made to the proposal?


Every time a human being or other mammal exhales, there is some carbon dioxide released into the air.


The conversion of methane to electricity would occur at a considerable distance from the landfills.


The methane that is used to generate electricity would generally be used as a substitute for a fuel that does not produce any greenhouse gases when burned.


Methane in the atmosphere is more effective in blocking the escape of heat from the Earth than is carbon dioxide.


The amount of methane emitted from the landfills could be reduced if the materials whose decomposition produces methane were not discarded, but recycled.

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