Reading ComprehensionDifficulty: Hard

PT146 S4 P4 Q26 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

Evaluate

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
26.

Based on the passage, the information yielded by which one of the following experiments would be most useful in determining whether a particular chemical could replace CFCs

Answer choices

  1. Unrelated to Goal2% picked this

    testing to see whether the chemical is capable of reacting with forms of oxygen

    We want to test whether the chemical would react with ozone, not stuff other than ozone.

  2. Unrelated to Goal9% picked this

    testing to see whether the chemical, when released into the lower atmosphere, would react with other

    We want to test whether the chemical would react with ozone in the stratosphere (upper atmosphere), not whether it reacts with other stuff in the lower atmosphere.

  3. Unrelated to Goal7% picked this

    testing the chemical to determine whether it would chemically react

    We want to test whether the chemical would react with ozone, not whether it reacts with chlorine. The goal of this chemical is to replace chlorine, so chlorine wouldn't even be in the picture anymore.

  4. Correct59% picked this

    testing to see what chemical properties the chemical or its constituent elements

    Why this is right

    We want to test whether the chemical would react with ozone the way chlorine reacted with ozone (by destroying the ozone). If we can see whether this potential replacement has chemical properties in common with chlorine that would cause it to react with ozone the same way, then we'll get the answer we're seeking. This answer is designed to be un-tempting by only talking about part of what we would want / need to know to make our assessment. We would not only need to know what chemical properties this potential replacement shares with chlorine, but we would also need to know which chemical properties of chlorine cause it to destroy ozone. But presumably the chemists doing chemical testing do know such stuff. Even though an answer to this question wouldn't give us the final verdict on its own, it's still a more valuable question to answer than any of the other answer choices.

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

  5. Not as Helpful as Correct Answer23% picked this

    testing the chemical to see if it would break down into its components when subjected

    This is tempting. If we tested the chemical and found out that it didn't break down into its components, would that show that it's harmless in the ozone layer? Not necessarily. It might not need to break down into constituent elements in order to react adversely with ozone. If it does break down into constituent parts, does that mean it would be harmful in the ozone layer? Not necessarily. Its constituent parts might not have any adverse reactions with ozone. Even though answering this question would be somewhat useful, it leaves us farther from a final verdict than would answering the question in (D). Ultimately what we care about the most is whether this replacement would react adversely with ozone. The question posed by (D) potentially reveals that answer, whether the replacement chemical breaks down into constituent elements or not, because the language of (D) covers the reactive possibilities of the replacement molecule as well as the reactive possibilities of the constituent atoms in the replacement.

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