Inhabitants of the country Orctania suffer from a much lower incidence

Its option C?

Everything else does or is aligned too
except C

­IMO Choice C

I was slightly confused between choices C and D. Tried my best to eliminate one choice. 

Conclusion - The incidence of cancer for outsiders, who take residence in Orctania, is radically higher that natives.
Evidence - Outsiders attempt to follow the practices of the natives, practices that natives follow, helping the natives suffer a much lower incidence of cancer.

Question type - Which of the following does not explain higher incidence in outsiders?
Eliminate the choices that help explain why outsiders settled in Orctania have higher incidence rates.

A. The causes of some forms of cancer that are prevalent in Orctania are genetic, not environmental or behavioral. Maybe few forms of cancer are dependent on the genetics which the outsiders lack, and hence it could be leading to higher incidence rates Incorrect

B. People from other countries who take up residence in Orctania may fail to succeed in following the practices of native Orctanians in important respects. Outsiders miss some crucial aspects of these practices, and this maybe helps us explain why they still have high incidence rates Incorrect

C. The non-native Orctanians who take up residence in Orctania tend to be motivated to do so by a desire to improve their health. Correct This choice gives us a reason why outsiders take up residence in Orctania, but fails to establish the link between the desire/ motivation and the incidence rates. This choice does not explain the lower incidence rates in outsiders.

D. It has not been established which one of several possible factors, or combination of these factors, is truly responsible for the low incidence of cancer in native Orctanians. This choice hints that there may be other factors that contribute to lower incidence, and not just environmental and behavioural factors. If we are not sure which factors lead to lower incidence, then we cannot be very sure on the reasoning that following a set of practices would lead to lower incidence. Hence, this choice explains the lower incidence in the outsiders by casting doubt on the reasoning Incorrect

E. Most non-natives move to Orctania too late in life to reap the environmental and behavioral health benefits of living there. This choice suggests by the age outsiders move into Orctania it is too late for them. Also, explains why outsiders still have higher incidence rates than natives Incorrect

Bunuel could please post an explanation for this CR. I am confused between C and D.

I feel D is the correct answer. Posted my response above.

Hi may you please help explain why its D not C ?

­Bunuel KarishmaB and other experts can you pls help 

I also chose C, but i get it why it is D.
C kind of says that, most non native already have cancer and thus move to the city to get cured.
Reject C.

D says it is not proven which ones help reduce cancer. Ok...so had it been proven can you still say,
that non natives did not practice those? So D kind of doesn't do anything to explain our query.
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OFFICIAL EXPLANATION:

Reading the question: we can see that this question looks like a lot of work. First, it has given us a difficult-seeming puzzle: this country is has a low cancer rate, for non-genetic reasons, but people who move there have a higher cancer rate. Secondly, we have a "NOT" question. Questions with "NOT," like those with "EXCEPT," tend to be labor intensive, since it's relatively slow to go through four good explanations and one bad one. The key technique here is to use a very basic filter. In "NOT" and "EXCEPT" questions--and all questions that are involved--you're often basic served by a basic filter.

Applying the filter: carefully asking this simple question, we can judge that (D) is the least explanatory of the cancer rate and is therefore the answer. In (D), even if the exact "factor" hasn't been determined, it doesn't matter, because the people who move to Orctania "attempt to follow the practices of the inhabitants." So, we don't know whether it's being pollution-free and stress-free and drug free and so on, but the people are doing all of them, so (D) doesn't help to clear up the mystery.Everything else is a good explanation. Choices (B) and (E) both point out that moving to the country does not automatically equate with enjoying the benefits of the environment or with adopting the behaviors. (C) points out that the population moving to the country might be doing so because they are unusually cancer-prone to begin with, which would explain why they would have a higher rate of cancer even after reaping benefits. Choice (A) points out the possibility that some forms of cancer aren't helped by living in Orctania--those kinds depend only on genes, and, critically, it's possible that the people who move to the country have genes more prone to those forms of cancer, somewhat like the case of (C).

Logical proof: finally, we can use a test of (D) that is similar to the negation test: say that it has been established which factor was responsible. That's not automatically an explanation, because, for all we know, the people who move to Orctania are perfectly recreating/copying that factor. Since the situation is unchanged given (D) or its negation, (D) is unimportant to the situation.

The correct answer is (D).