The conclusion of the initial proposal is that "the methane now emitted from open landfills should instead be burned to produce electricity." In other words, the methane from landfills should be burned to produce electricity, preventing the methane from entering the atmosphere. Why do this? Because methane in the atmosphere blocks the escape of heat and contributes to global warming. If we want to reduce global warming, we should reduce the amount of methane emitted into the atmosphere. Burning the methane from landfills would accomplish this goal, according to the proposal.

This proposal is then met with an objection. The person making the objection does not dispute that burning methane from landfills would reduce emission of methane into the atmosphere. However, because burning methane generates carbon dioxide (another greenhouse gas), reducing methane emissions in this way would increase emissions of another greenhouse gas (carbon dioxide). In other words, the proposed method of reducing emissions of one greenhouse gas (methane) would simply increase the emissions of another (carbon dioxide). Now we need to select a statement that, if true, would counter this objection:

The proposal in the passage -- and the objection to that proposal -- are related to the burning of methane emitted from open landfills. But the proposal and the objection have nothing to do with the amount of carbon dioxide released by humans and other mammals when they exhale. This statement does not counter the objection in the passage, so (A) can be eliminated.

Regardless of where the methane is burned to produce electricity, the conversion process would still presumably generate carbon dioxide emissions that would enter the atmosphere. Thus, the distance from the landfills does not counter the objection, and choice (B) can be eliminated.

Remember, the objection is that "the burning of methane generates carbon dioxide that is released into the atmosphere." If anything, choice (C) strengthens the objection. The burning of methane will generate another greenhouse gas (carbon dioxide) that contributes to global warming, AND this methane will be used as a substitute to replace a fuel that does NOT produce any greenhouse gases and thus does NOT contribute to global warming. Thus, this statement presents another drawback of burning methane to produce electricity, and choice (C) can be eliminated.

The objection is that the proposed method of reducing emissions of one greenhouse gas (methane) would increase the emissions of another greenhouse gas (carbon dioxide). However, choice (D) tells us that methane is MORE effective in blocking the escape of heat than is carbon dioxide. If we are trying to reduce global warming, we would certainly rather have carbon dioxide in the atmosphere than methane, since carbon dioxide traps less heat and thus contributes less to global warming than methane does. The objection implies that burning the methane will NOT reduce global warming because it will simply replace one greenhouse gas with another. However, choice (D) effectively counters this objection by stating that having carbon dioxide in the atmosphere is better than having methane in the atmosphere, if we want to reduce global warming. Choice (D) looks good.

Regardless of the amount of methane emitted from open landfills, the proposal is that this methane should be burned instead of being allowed to enter the atmosphere, and the objection is that burning the methane will create another greenhouse gas (carbon dioxide). Reducing the amount of methane would not impact either argument, so choice (E) can be eliminated, and (D) is our answer.