Doctors in county X opine that they need to redefine the minimum

OFFICIAL EXPLANATION

According to the statement there is a need to redefine the parameters of threshold levels of blood sugar, blood pressure and cholesterol in the country.

(A) states that there are persons who have higher levels of these but do not have heart diseases.

(B) does not strengthen or weaken the argument. It's irrelevant

(C) is not correct as a hereditary factor is one of those which show a potential for heart diseases.

(D) and (E) do not give reasons for changing the prescribed threshold levels of the various parameters.

Hence (A) is the correct answer.

I am not sure how valid this question is, since it's without a source, but I will do my best:

A) Good choice. If this is the case, then it gives a reason why the levels need to be changed. If you have a large number of people who, without the other risk factors (obesity/hereditary), are above the current levels but are not suffering from heart disease, then clearly the levels are inaccurate, and should be adjusted.

B) This can go either way. Either it shows that the levels are set "too high" and people do not take tests because they are not healthy, or the levels are correct but the doctors think they are wrong because of a lack of data. Too broad, out.

C) Tricky. This discusses a specific set of people. This is not who the levels are aimed for, as the passage says "three major factors apart from obesity and hereditary factors". It would be normal to have a situation in which people with the other factors still get heart disease, even if their blood levels are below the current requirements. Out.

D) Not relevant at all. Sure, it maybe explains why doctors feel the need to change the levels, but it does not affect the argument.

E) Similar to D, this explains rather than strengthens. Out.

Hope that helps!