Reading ComprehensionDifficulty: Medium

PT146 S4 P4 Q23 Explanation

Chlorofluorocarbons and the Ozone

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Passage

By 1970 it was well established that ultraviolet light from the sun contributes to skin cancer. Fortunately, much of the sun’s most damaging ultraviolet radiation is screened out by a thin, diffuse layer of ozone—a toxic to 25 miles above the earth’s surface.

During the 1970s, however, public policy makers worldwide were alerted to the fragility of the ozone layer through the pioneering research and advocacy of two Nobel Prize-winning scientists, Mario Molina and F. Sherwood Rowland. In the absence of pollutants, stratospheric ozone concentrations should remain stable over time, with natural production and destruction chemical reaction, each chlorine atom could destroy as many as 100,000 ozone molecules before becoming inactive.

In 1974 the two scientists estimated that the atmosphere contained the accumulation of five years of global CFC production. This meant that, given the rate of diffusion and breakdown of CFCs in the atmosphere, the depletion of the ozone layer would continue for years, if not decades, even if the production and Congress and was later appointed to the U.S. National Science Foundation Committee on Fluorocarbon Technology Assessment.

Predictably, the work of Molina and Rowland and their advocacy of dramatic policy changes were subjected to attacks by critics, especially scientists with ties to the CFC industry. However, over time their views were corroborated, especially by the discovery of a hole in the ozone layer over Antarctica, and this led to in packaging for consumer spray products and the development of more environmentally friendly refrigerant chemicals.

What this question is testing

Five Questions

Your task

Pin down exactly what the question asks about the passage — a detail, the author's view, the structure, or the main point — before looking at the choices.

Common trap

Answers that restate a true detail from the passage but don't answer the specific question being asked.

Winning move

Anticipate the answer in your own words from the passage, then find the choice that matches that prediction.

Reading along? Open the full official question in LawHub — we show a fragment here and keep the reasoning in our own words.

The question
23.

The information in the passage most helps to answer which one of

Answer choices

  1. Out of Scope: laboratory experiments11% picked this

    What laboratory experiments were conducted by Molina or Rowland in their

    In the 2nd paragraph, we're told that M & R studied two types of CFCs and observed how they behave in the lower atmosphere and stratosphere. But that sounds more like a field observation. We don't hear anything about laboratory experiments.

  2. Out of Scope: concentration3% picked this

    What was the estimated concentration of CFCs in the atmosphere

    1987 is only mentioned once in the final paragraph and there's nothing in there that spells out any concentration of CFCs.

  3. Out of Scope: year of testimony4% picked this

    In what year did Molina testify before the

    We know from the 3rd paragraph that Molina and Rowland "became public advocates" starting around 1974 and that Molina was invited to testify before Congress. But we don't know if that was in 1974 or one of the following years.

  4. Out of Scope: non-chlorine destroyer7% picked this

    Does any chemical that does not contain chlorine contribute to the destruction

    The only destroyer of ozone molecules we hear about is chlorine. There may be others; there might not be, but we can't say. The passage never told us that "only chlorine can contribute to the destruction of ozone molecules".

  5. Correct76% picked this

    Which constituent element of CFCs is most damaging

    Why this is right

    The most damaging ingredient is chlorine! We're told that, "once in the stratosphere, CFCs break down into their constituent elements, including chlorine. The resulting increase in the concentration of chlorine in the stratosphere is devastating to the ozone layer (because each chlorine atom could destroy as many as 100,000 ozone molecules." Nothing in that text specifically spells out that chlorine is the most damaging part of a CFC, but it's highly, highly suggested. If there were some other ingredient in CFCs that was even worse for the ozone layer than chlorine is, wouldn't this passage have mentioned it? It would be highly relevant to the conversation. It would go very much against common sense that the author would fail to mention a part of CFC's that is even more devastating to the ozone layer.

    Skill tested: Five Questions · how this choice captures the passage's function is the move to repeat next time.

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