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Complete Question Explanation

Must Be True. The correct answer choice is (E)

This is a rather complex stimulus dealing with the potentially beneficial effects of repowering factories with clean-coal technologies. The primary effect discussed is the reduction of pollutants involved in acid rain formation, specifically sulfur dioxide and nitrogen oxide. We are then told in the final sentence that a reduction in the amount of emitted nitrogen pollutants would reduce noxious oxide in the troposphere. The only real inference to be drawn from this seems to be a near restatement: clean-coal technologies can reduce the amount of certain substances in the troposphere.

While this stimulus does provide us with some useful information about the connection between clean-coal technologies, polluting emissions, and some specific chemical pollutants, what is perhaps more important is what this stimulus does not tell us. That is, we really do not know much about how these how these chemicals are formed or emitted, what role they play in the formation of acid rain, or even how clean-coal technologies will be implemented to counteract this pollution. So be particularly wary of answer choices that go beyond the information provided in the stimulus and attempt to make assumptions about the details provided.

Answer choice (A): There is no way to know that sulfur dioxide emissions are the most dangerous pollutants implicated in acid rain. While they seem to play a part in acid rain formation, to compare them to all other pollutants involved is impossible.

Answer choice (B): We do not have any information on specifically how noxious ozone is formed, and what little information we do have connects noxious ozone to nitrogen pollutants/nitrogen oxide, not sulfur dioxide. Further, the stimulus discusses noxious ozone formed in the troposphere, while this answer choice deals with the formation of noxious ozone in factories.

Answer choice (C): While the stimulus does state that it may be possible to cut sulfur dioxide emissions by more than 80 percent, there is no way to conclude anything about how harmful the remaining 20 percent would be. The notion of what constitutes “harm” or a “harmful level” is never addressed in the stimulus.

Answer choice (D): A substantial reduction of polluting emissions seems to be a possible benefit of using clean-coal technologies in factories, but to conclude that this will be achieved by redesigning factories is an assumption that cannot be known. Plus, the stimulus discusses redesigning existing factories whereas this answer references "new" factories, which we do not know anything about.

Answer choice (E): This is the correct answer choice. As mentioned above, the connection in the stimulus is that choosing to use certain technologies (clean coal) could reduce the formation/amount of noxious ozone in the troposphere.
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Does this stimulus have conditional reasoning in it? While it's not really relevant or necessary to getting the correct answer choice, I want to make sure that I'm noticing when a sentence has a conditional relationship.

When the author states "using clean-coal technologies..." I took this to mean that if, or, every time clean coal technologies is used in existing factories, we see a reduction of polluting emissions. Therefore, via the contrapositive, if there is no reduction or an increase of polluting emissions, then clean coal technologies aren't being used in the existing factory.

I diagrammed the following as such: Clean coal technologies used :arrow: Reduction of polluting emissions.

Of course, I would be diagramming each conditional on test day but in practicing I want to make sure that I'm realizing when a conditional relationship is present.
 Paul Marsh
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Hi Andriana! Your instinct to always be on the lookout for diagramming conditional reasoning is a good one. Many test-takers fail to recognize situations when diagramming out the conditionals in a stimulus would be very helpful. I think that as you're learning to recognize those situations, it's not a bad thing to err on the side of looking too much for diagramming conditional reasoning. Over time and through practice, you'll be able to recognize when diagramming conditionals will help you and when it won't.

This question falls into the latter category. The sentences do not all neatly fit into conditionals, and we don't gain much from trying to diagram them out. Though if you were to make a conditional diagram of the first part of the first sentence of the stimulus, then it would look exactly like your diagram. And your contrapositive is right on the money as well. So it looks like you're doing a very good job of understanding how conditionals work!

Ultimately, diagramming conditional reasoning is a tool to help you quickly and correctly navigate the logical inferences of conditional sentences. As mentioned above, you seem to have a nice grasp of how to use that tool. But knowing when to use that tool is something different. Just because a tool can be used, doesn't mean it always should be. Sometimes, diagramming the conditionals will save you time and help you make inferences that would otherwise be difficult to see. Or in other instances, diagramming makes it easier to find a Parallel answer choice that uses similar conditional reasoning. In those cases and many others, using the tool is the right move. But there are other times when trying to diagram everything will be needlessly confusing and overly time-consuming. A good starting point is to look out for the classic sufficient condition and necessary condition indicators (from Lesson 3 in the Course books). As you're practicing questions that use conditional reasoning, ask yourself, "Did diagramming these conditionals help me to reach the correct answer? If so, how?" If you take the time to critique and analyze your use of conditional diagrams, eventually you'll be very comfortable with knowing when to draw out the conditionals and when not to.

This nicely written blog post from PowerScore talks more about the subject: ... o-diagram/

Hope that helps!
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I selected D, but it was a guess between that answer choice and E. The last answer choice seemed like it could be correct, but "the choice of technologies" sounded too vague to me. But I see that one of my mistakes with choosing D is that "will" is too strong and that the first sentence talks about the existing factories, whereas D discusses new factories. Please let me know what you think of my logic.
 Robert Carroll
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If "choice of technologies" is vague, that seems to be a good thing. If the phrase is vague, it can cover a lot of things, like the specific thing discussed by the stimulus. So that cannot be an objection to answer choice (E). The fact that answer choice (D) discusses new factories is a fatal problem for it.

Robert Carroll

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