Hi Haley,
Thanks for the question! Let's first break down the argument, and then we'll take a closer look at answer choice (D).
The stimulus sets up a scenario where a local government ran an antismoking advertising campaign. This campaign was financed by taxing cigarettes at 20 cents per pack. A year later smoking was down 3%, and so the author concludes that the cause of the decline was the advertising campaign.
Now, the first thing to realize is that this is a causal argument. The author sees two things happening in succession, and concludes that the first caused the second. If we wanted, we could capture that using a causal diagram:
- Cause Effect
antismoking advertising campaign decline in number of smokers.
The relationship doesn't have to be diagrammed, though. I just did that so it was as clear as possible.
Second, when you read that argument, what's your reaction? Are you fully convinced that the author's conclusion is valid? Did you see any weakness in that argument? When I read that problem, I thought to myself, "How does the author know it's the advertising campaign that worked? If they raised the price by 20 cents, maybe the higher cost caused people to smoke less."
When I see that's it's a strengthen question, I'm not in trouble: I can still use the prephrased weakness that I saw. But instead of just using it as-is (which would hurt the argument), instead I would love an answer that eliminates that weakness. In basic causal arguments, if you eliminate an alternate cause, that strengthens the argument.
Answer choice (D) does just that. When I read the stimulus I saw an alternate cause for the conclusion, namely that it might have been the higher price that reduced the number of smokers. Answer choice (D) eliminates the higher price as a possible cause, because if the merchants absorbed the cost of the tax (which is essentially what happens when they reduce the price 20 cents), then the cost of a pack of cigarettes remained the same as before. If the price was the same, that means that cost wasn't a factor here. In abstract terms, (D) eliminates an alternate cause for the conclusion, and thus strengthens the argument.
Overall, this is a great question because it allows you to see how one of the fundamental reasoning/question type relationships on the LSAT works (strengthening a causal conclusion by eliminating an alt cause). So, I really want to make sure this makes total sense for you. If you have any questions, please let me know. Thanks!