Reading Comprehension

PT146 · S4 · P4 · Q23 Chlorofluorocarbons and the Ozone

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By 1970 it was well established that ultraviolet light from the sun contributes to skin cancer.

Topic

The effects of chlorofluorocarbons (CFCs) on ozone depletion and the resulting public policy response.

Framework

Problem / Solution

Main Point

Molina and Rowland discovered that CFCs deplete the ozone layer, which protects us from cancer-causing ultraviolet radiation, prompting international policy change to control these pollutants. (Paragraph 2) This is wrapped up in Paragraph 4, where it summarizes the outcome:

P1: Importance of the Ozone Layer

By 1970, it was understood that ultraviolet radiation from the sun can cause skin cancer, but thankfully Earth's ozone layer filters out much of this harmful radiation.

P2: Discovery of the Ozone Problem

Scientists Molina and Rowland revealed that man-made chemicals called CFCs, found in products like aerosols and refrigerants, break down in the upper atmosphere and release chlorine, which destroys ozone. A single chlorine atom can wipe out thousands of ozone molecules.

P3: The Lasting Threat and Call to Action

Their research showed that even if we stopped using CFCs immediately, the chemicals already present would keep damaging ozone for many years. Molina and Rowland pushed for urgent public policies to address this environmental danger, leading to political attention and involvement in research committees.

23.

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

  1. What laboratory experiments were conducted

    Out of Scope: laboratory experiments

    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.

    11% picked this

  2. What was the estimated concentration

    Out of Scope: concentration

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

    2% picked this

  3. In what year did Molina

    Out of Scope: year of testimony

    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% picked this

  4. Does any chemical that does

    Out of Scope: non-chlorine destroyer

    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".

    6% picked this

  5. Correct

    Which constituent element of CFCs

    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.

    77% picked this

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