Proposal: Carbon dioxide and methane in the atmosphere block the escape of heat into space. So emission df 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?

Consultant: Ace Repairs ends up having to redo a significant number of the complex repair jobs it undertakes, but when those repairs are redone, they are invariably done right. Since we have established that there is no systematic difference between the mechanics who are assigned to do the initial repairs and those who are assigned to redo unsatisfactory jobs, we must reject the hypothesis that mistakes made in the initial repairs are due to the mechanics' lack of competence. Rather, it is likely that complex repairs require a level of focused attention that the company's mechanics apply consistently only to repair jobs that have not been done right on the first try.

In the consultant's reasoning, the two portions in boldface play which of the following roles?

Scientists claim that the discovery of the first authenticated mammal bones in amber could provide important clues of determining, in addition to how, when mammals colorized the islands of the West Indies.

Even with the proposed budget cuts and new taxes and fees, the city's projected deficit for the next budget year is getting worse: administration officials announced that they believe the gap will be $3.7 billion, a billion dollars over what it was predicted just two months ago.

Because property values sometimes fluctuate in response to economic conditions beyond the purchaser's control, an investment in a home may underperform when compared to that of other widely available classes of investments.

Scientists say that, by bathing the skin cells in extracts of immune cells, that human skin cells in a test tube are made to behave as if they were immune system cells.

Analysts and media executives predict the coming year to be no less challenging than the previous one had been for the company’s C.E.O.

Educator Maria Montessori believed that students be allowed to choose from among a number of different lessons designed for the encouragement of their development as thinkers and creators with individual learning and thinking styles.

Which of the following most logically completes the passage?

Laminated glass is much harder to break than the glass typically used in the windows of cars driven in Relnia. It is more difficult for thieves to break into cars with laminated glass windows than into cars with ordinary glass windows, and laminated glass windows are less likely to break in a collision. Nevertheless, considerations of security and safety do not unambiguously support a proposal to require that in Relnia all glass installed in cars be laminated glass, since_________.

In an attempt to produce a coffee plant that would yield beans containing no caffeine. the synthesis of a substance known to be integral to the initial stages of caffeine production was blocked either in the beans, in the leaves, or both. For those plants in which synthesis of the substance was blocked only in the leaves. the resulting beans contained no caffeine.

Any of the following. if true, would provide the basis for an explanation of the observed results EXCEPT: