agrasan
I wanted to confirm my reasoning on option C
Even though "
incidence" means occurrence/rate/frequency
(https://dictionary.cambridge.org/dictio ... /incidence), the conclusion talks about
"risk of cancer", and option C talks about
cancer deaths which is a shift in scope, hence, no impact on the conclusion.
Someone earlier in the thread wrote that this is an official GMAT problem, and it is not -- it's a very old LSAT problem. And it's a low-quality problem at that. For one thing, half the stem is redundant (naturally if cancer incidence is higher as fat intake goes up, cancer incidence is lower as fat intake goes down -- there's no need to say that), and answer C uses the word "prominent" in a bizarre way.
I'm not really sure why answer C would be tempting here. Premises in CR questions are premises. We know that as fat intake goes up, cancer incidence goes up. Even if C said
Cancer is very common in countries with low fat intake, we would absolutely know from the stem that cancer is
even more common in countries with high fat intake. Premises cannot be false. But as you point out, answer C does not even talk about cancer incidence. It talks about cancer deaths, and the argument has nothing to do with cancer deaths, so answer C does nothing to weaken the conclusion.
This is a classic correlation/causation argument, and we can weaken any argument like this by finding an alternate cause. Answers B and D are the only contenders, because they both suggest that high fat intake countries are different from low fat intake countries in meaningful ways other than fat intake. So there might be another explanation for the correlation described in the stem. I would happily choose answer B here if answer D was not there, but D is better because pollution could directly cause cancer, while the wealth mentioned in answer B cannot (though it might be true in wealthy countries that people are exposed to more risks, e.g. to more radiation from technology, say, which is why B is the clear second-best answer here).