Nuclear reactors are sometimes built in "geologically quiet" regions, so called by geologists because such regions ar...

Selin on July 27, 2020

Can you please explain

Why is C the correct answer and how can we get to that assumption?

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Shunhe on July 29, 2020

Hi @schicago,

Thanks for the question! So let’s walk through the argument first. We’re told that nuclear reactors are sometimes built in quiet regions that have only minor faults and are away from plate boundaries. We’re also told that no minor faults in quiet regions produce earthquakes more often than once in 100,000 years. The argument then concludes that if you take all the potential nuclear reactor sites in a region, the ones least likely to be struck by an earthquake are the ones that are located near a fault that’s recently produced an earthquake.

So now we’re being asked for a necessary assumption of the argument. Take a look at (C), which tells us that in a geologically quiet region, every potential nuclear reactor site is near at least one minor fault. Let’s use the assumption negation test to see if this is necessary: in a geologically quiet region, not every potential nuclear reactor site is near at least one minor fault. In other words, there’s at least one potential nuclear reactor site that’s not near a minor fault. Well, if this is true, and there’s no minor faults or plate boundaries near a location, isn’t that place the least likely to be struck by an earthquake? Since even a minor fault is more likely to have an earthquake than a place with no faults. If we negate (C), the argument falls apart, since the nuclear reactor sites away from all faults would be the least likely to be struck by an earthquake, not the ones near minor faults that have recently gone off. And since that’s the case,

Hope this helps! Feel free to ask any other questions that you might have.

Landi on November 3, 2020

In the passage it states that geologically quiet regions contain only minor faults which led me to infer that the minor faults are already present in all geologically quiet regions. Please explain.