Chlorofluorocarbons and the Ozone

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TopicsInferenceScience

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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

Inference

Your task

Find what must be true based on what the passage or stimulus states.

Common trap

Answers that are plausible or likely but not actually guaranteed by the text.

Winning move

Keep only the choice the statements fully support — eliminate anything that requires an extra assumption.

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

The question

27.

Which one of the following statements is most strongly supported by the information

Answer choices

Too Strong: no3% picked this
No refrigerant chemicals other than CFCs had been discovered when Molina and Rowland suggested that
We were told that some CFCs were refrigerants. This answer is saying that "all known refrigerants are CFCs". We can't support that anywhere in the passage.
3%
Correct68% picked this
Refrigerant chemicals developed as substitutes for CFCs after 1987 release fewer chlorine atoms into the
Why this is right
This is supported by the final sentence, as well as more broadly by the whole point of the passage. CFCs were discovered to be terrible for the ozone layer because they broke down into chlorine atoms. A chlorine atom in the stratosphere would kill 100,000 useful oxygen atoms, thus depleting that layer of ozone. We know from the story of this passage that eventually this discovery translated into action. CFCs were banned in the late 1970s and naturally they would be replaced by something less harmful to the ozone layer (since that's the whole reason for the ban). The final sentence says that once CFCs were banned in the late 1970s, it led to more environmentally friendly refrigerant chemicals. In what sense were these new refrigerant chemicals more environmentally friendly? The passage doesn't specifically say, but since these new chemicals were designed as a response to the CFC's, which were damaging because of the chlorine atoms they released into the stratosphere, it's common sense to think the passage is saying, 'these new refrigerants were not as bad when it came to releasing chlorine atoms into the stratosphere".
Skill tested: Inference · how this choice captures the passage's function is the move to repeat next time.
68%
Too Strong: most Unsupported Causal Relationship4% picked this
CFCs were originally used in refrigeration components because they provided the most energy-efficient
We were never told why CFC's were originally used. Maybe it was because they provided the most energy-efficient means of refrigeration. Maybe they provided the 2nd most energy-efficient means but they smelled better, or they were easier to make cheaply. We have no idea.
4%
Contradicted20% picked this
The Montreal Protocol led to the cessation of CFC production in
The final two sentences suggest the opposite of this. The Montreal Protocol wasn't until 1987, but we're told that North America ceased CFC production in the late 1970s, when CFC's were banned.
20%
Out of Scope: manufactured today6% picked this
Some of the refrigerant chemicals being manufactured today contain chemicals known to
We never hear about any refrigerant chemicals made today, so we have no support to say anything about them.
6%

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