Reading comp PrepTest 146 · Section 4 · Question 26

Incorrect. The ozone layer is made up of ozone, so whether a chemical reacts with other types of oxygen isn't known to be relevant here.

Incorrect. (Lines 22-26) The science-y portion of Paragraph 2 notes that it's not until the CFCs drift up to the upper atmosphere and get hit with UV radiation that they break down and cause damage, so checking the new chemical just in the lower atmosphere wouldn't show whether it does damage similar to CFCs.

Incorrect. (Lines 24-26) Chlorine is a constituent element of CFCs—not a chemical with which CFCs react.

Correct. Question Type:
Argument Evaluation

Strategy Overview:
Identify the key element of CFCs that made them damaging to the ozone layer, then find an answer that would relate any potential replacements to that cause

Answer Anticipation/Relevant Lines:
While the science of Paragraph 2 may have been confusing, what with tropospheres and stratospheres and atoms and molecules, the overall takeaway wasn't—CFCs deplete the ozone layer because they have chlorine that gets released when they break down. The chlorine was the key to the damage being caused, according to the passage.

As such, if we're looking for a replacement, we'd want to know if it has chlorine or a chemical that has the same effects on ozone as chlorine. Let's find an answer that addresses that.

Answer Explanation:
(Lines 26-33) The "devastating" effects of CFCs on the ozone layer are largely tied to chlorine, each atom of which can take out 100,000 ozone molecules. As such, seeing if the new chemical or any constituent element is similar to chlorine would be helpful in analyzing whether it, too, would have devastating effects. This answer is therefore correct.

Key Takeaway:
Science passages can get pretty technical, and they can throw around a lot of tough verbiage, but the basic relationships tend to be more straightforward. Here, the passage went to great lengths to point out that chlorine was the key "ingredient" that made CFCs bad for the ozone layer, and that's all we needed to take away from the passage to get this question correct.

Incorrect. (Lines 26-33) This answer is tempting! After all, figuring this out would tell us if the chemical is in a certain way similar to CFCs. However, there are a couple problems here. First, CFCs damage the ozone layer not because they break down, but because when they break down they release chlorine. If another chemical breaks down but into harmless chemicals, then it wouldn't hurt the ozone layer. Second (the flipside of the first point), there's no indication that a chemical that doesn't break down wouldn't harm the ozone layer. If we replaced CFCs with pure chlorine, that would be bad for the ozone layer. This answer focuses on something about CFCs that isn't directly tied to the harm they do, so it's incorrect.