Consuming gluten, a protein composite found in foods processed from

A. The number of doctors specializing in nutrition in our country has not decreased over the past four years.

B. Adults who are allergic to gluten are no more likely than other adults to have allergies to other food ingredients.

C. Adults who have allergic reactions to gluten are not more likely to be see a doctor for treatment now than they were four years ago.

D. In our country, either more gluten has been introduced into foods artificially, or adults have eaten more food naturally containing gluten.

E. The percentage of the population in our country of adult age has not changed relative to four years ago.

According to me C should be the answer.
Option C very clearly holds the main pillar to the conclusion.
If C is considered false then the conclusion wont hold.

I eliminated option A , B, and E. Whereas, i was confused in between options C and D at first but with the help of resources.
I conclude option C is the answer
"option C infers that the number of people (allergic to gluten) seeing doctor now does not change compared to the levels of 4 years ago" - so the sample size is same and now as more people shows positive medical record of allergic to gluten. Supports the conclusion of the argument.
Whereas, option D is just a restatement of the conclusion.

I went for C, I kind of thought of thats the assumption even before i read it.

I chose C, but I think E can be answer too.

Assumption means 'necessary condition', and we can find it by doing negation test.

(E) (negated) The percentage of the population in our country of adult age has changed relative to four years ago.

if above is true, the conclusion of the argument is weakened.

- the argument is saying [the percentage of adults in our country who have seen a doctor for gluten allergies has increased significantly in the last four years.]

- but, what if the total number of adult(=1. see a doctor for allergy + 2. the rest) has decreased while the number of adults who 1. see a doctor for allergy remain the same as 4 years ago?

- even though, It suffice the fact that [the percentage of adults in our country who have seen a doctor for gluten allergies has increased significantly in the last four years.]

- however, the conclusion [Either our adults have been exposed to more glutens, or they have developed a greater sensitivity to them.] can be wrong(=weakend) because there should be demographic cause for the percentage increase.

so, E can be answer too.

E can not be the answer because we looking for percentage of people seeing the doctor.
lets say right now the pollution is 100 and 10 % people are seeing the doctor and 4 years later population rise up to 200 and now 20 people (which is again 10 % only) are seeing the doctor.

Hence overall option E is irrelevant as an answer choice

How about the situation like this?

	4 years ago	Current
Total population	100	50
- adult population	20	20
- adult who see a doctor for allergy	10	10

in this situation, [the percentage of adults in our country who have seen a doctor for gluten allergies has increased significantly in the last four years.] (10% -> 20%)

but the proportion of the number of adult who see a doctor for allergy to the total number of adult remain as 50%

so we can't say it's because [Either our adults have been exposed to more glutens, or they have developed a greater sensitivity to them.]

However, in considering (E), table above shoud be changed like this

	4 years ago	Current
Total population	100	50
- adult population	20	10
- adult who see a doctor for allergy	10	10

in this case, the proportion of the number of adult who see a doctor for allergy to the total number of adult rose to 100% from 50%

So we can say [Either our adults have been exposed to more glutens, or they have developed a greater sensitivity to them.]

The word play lies in - percentage of adults who have seen a doctor

So as per your table: % of Adults (20) who see a doctor (10) become 50% and remains same in the next year as well. But the question mentions that this percentage has changed.

E) talks about the adult population out of the total population which doesn't really matter since the aforementioned metric is what we are really focussing on

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Official Explanation

Reading the question: we read the prompt and find a somewhat hasty argument. The first two statements are facts, while the last one is an opinion and is the conclusion. One weakness here is that the author has allowed for only two possibilities. There might be another possibility. And that makes us notice: we have a causal argument! So we will look for a different cause in the answer choices--for the increased percentage of adults who have seen a doctor for gluten allergies. Specifically, given the format of the answer choices, which one rules out a new cause for increased visits? That's our filter.

Applying the filter: (A), (B), and (E) all rule something out, but the things they rule out wouldn't cause more gluten visits. Choice (C) rules out something that would cause more gluten visits, so it looks correct.

Logical proof: Negating (C) proves it: if people with the allergy are more likely to go in, that could be a different reason than given in the conclusion and the argument would be weakened or broken. Meanwhile, choice (D) does not pass the negation test; it merely states a possibility.

The correct answer is (C).­