Hi Rahim,
Welcome to the Forum (from our great class together
), and good question! I'm assuming you're asking about the correct answer here, answer choice B, so I'll focus my comments on that. But let us know if that's incorrect.
Let's break down the answer choice, starting with the introductory language, which says, "presumes, without providing justification, that..." What this means is that the argument assumes something it hasn't provided evidence or premises for ("presumes" being a synonym of "assumes," and "justification" being evidence or premises). So we need to figure out whether the argument did actually assume (and give no evidence for) what the answer choice discusses.
Now let's look at the rest of the answer, which reads, "ozone-related health costs in the city vary roughly in proportion to ozone levels." This means that health costs from ozone issues tend to track with ozone levels. In other words, roughly speaking, when ozone levels go up by a certain proportion (say, 20%), the health costs from those levels also go up by about the same proportion (about 20%). When ozone levels go down by a certain proportion (say, 20%), the health costs from those levels also go down by about the same proportion (about 20%).
So the question is whether the argument assumed, without giving evidence, that changes in ozone levels track roughly with changes in ozone-related health costs. The argument does assume that! How do we know? Because the premise in the first sentence tells us that implementing pollution measures would
decrease ozone levels (by about one fifth). And the conclusion tells us that implementing these measures would therefore
decrease health costs from ozone issues by about one fifth ($1 billion less than the current $5 billion level). And there's no evidence or premises provided that ozone levels actually (in fact) track roughly with ozone-caused health costs. So answer choice B is our answer.
I hope this helps!
Jeremy Press
LSAT Instructor and law school admissions consultant
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