I also selected answer choice C. But the official answer is D.
This is an LSAT question. So, I donтАЩt suspect the quality of the question.
Here is my guess.
This question is testing our understanding of correlation vs causation.
The argument does not mention that fat causes cancer. What it says
is that there is a high incidence of cancer death in countries where
the fat intake is more.
(B) OOS [= Out of Scope ]
(C) Cancer is a prominent cause of death in countries with a low average fat intake.
This answer choice comes second to answer choice D.
It is talking about other countries, which may or may not be relevant to the country in discussion.
(D) The countries with high average fat intake are also the countries with highest levels of environmental pollution.
The argument says cancer and fat in take are correlated.
But, this answer choice adds another variable in to the
Correlation relation, and that new parameter is pollution.
Cancer deaths are positively correlated with fat intake. << From the argument
Cancer deaths are positively correlated with pollution. << From answer D
So, there could be at least two causes and we don't know
which one is causing the cancer.
(E) An individual resident of a country whose population has a high average fat intake may have a diet with a low fat intake.
One person out of 100 million people << Statistics always ignores