undermines the conclusion

gmatnmein2010 wrote:It is proposed to allow the sale, without prescription, of a medication that physicians currently prescribe to treat the common ear inflammation called "swimmer's ear." The principal objection is that most people lack the expertise for proper self-diagnosis and might not seek medical help for more serious conditions in the mistaken belief that they have swimmer's ear. Yet in a recent study, of 1,000 people who suspected that they had swimmer's ear, 84 percent had made a correct diagnosis - a slightly better accuracy rate than physicians have in diagnosing swimmer's ear. Thus, clearly, most people can diagnose swimmer's ear in themselves without ever having to consult a physician.

Which one of the following, if true, most undermines the conclusion?

Conclusion : Most ppl can diagnose swimmer's ear in themselves without ever having to consult a physician

The author has come to the above conclusion (most ppl) by sampling few ppl (1000 ppl)
We can weaken the argument by showing some kind of disparity in the data/characteristics of the group sampled.

A) Case in which swimmer's ear progresses to more serious infections are very rare.
Incorrect : This does not help in weakening the argument in any way.

B) Most of those who suspected incorrectly that they had swimmer's ear also believed that they had other ailments that in fact they did not have.
Incorrect : Other ailments is clearly irrelevant to the scope of the argument.

C) Most of the people who diagnosed themselves correctly had been treated by a physician for a prior occurrence of swimmer's ear.
Correct : Weakens the argument by showing that most ppl who diagnosed themselves correctly had previously been treated by a physician and hence they had knew about symptoms of swimmer's ear.

D) Physicians who specialize in ear diseases are generally able to provide more accurate diagnoses than those provided by general practitioners.
Incorrect : General Practitioners v/s Ear Specialists is out of scope

E) For many people who develop swimmer's ear, the condition disappears without medical or pharmaceutical intervention.
Incorrect : Issue is not about treating swimmer's ear, issue is about diagnosing swimmer's ear. Eliminated.