PT42, S4, Q20 - A recent study suggests that

[jefyuan]

I don't understand the reasoning behind answer choice A.

[ManhattanPrepLSAT1]

This one's pretty tough.

This is an Identify the Flaw question. We need to figure out where the argument goes wrong. The critics conclusion is that "drinking three glasses of wine daily would not benefit health overall." The evidence they have for this is that the "decrease in the risk of stroke associated with that level of consumption is negated by its associated increased risk of sudden heart attack."

The devil here is in the details. The new study is suggesting 3 glasses of wine daily. The increased risk of sudden heart attacks is only established for "binge drinkers" - people who drink 3 glasses or more but only once per week. The new study is recommending 3 times daily. Maybe binge drinkers who drink more than 3 glasses on average end up drinking more like 12 drinks when they go out. Maybe there's something about having drinks every day (as the new study is suggesting) that is much healthier than only have drinks once per week (as the definition of "binge drinkers" includes). Either way, this argument has overlooked a potential significant difference between the two groups.

They're comparing apples and oranges. Current binge drinkers don't represent what the new study is advocating. So while binge drinkers might have an increase risk of sudden heart attack, following the new study's recommendation might not.

(A) is correct. The argument does attribute consequences of binge drinking (increased risk of sudden heart attack) to people whose regular consumption of wine is three glasses a day (those who follow the new study's recommendation.
(B) is not correct. The argument is pretty clear about the different kinds of health risks. For example it distinguishes between sudden heart attacks and stroke.
(C) is not true. The argument does assume that there is not a specific difference between wine and other sorts of alcoholic drinks with respect to the increased risk of sudden heart attack. But the argument doesn't assume that there is no significant difference in terms of health benefits and risks in general.
(D) is true but does not describe a flaw associated with the argument.
(E) is true but does not describe a flaw associated with the argument.