Eating garlic reduces the levels of cholesterol and

Eating garlic reduces the levels of cholesterol and triglycerides in the blood and so helps reduce the risk of cardiovascular disease. Evidence that eating garlic reduces these levels is that a group of patients taking a garlic tablet each day for four months showed a 12 percent reduction in cholesterol and a 17 percent reduction in triglycerides; over the same period, a group of similar patients taking a medically inert tablet showed only a 2 percent reduction in triglycerides and a 3 percent reduction in cholesterol.

It would be most important to determine which one of the following in evaluating the argument?

(A) whether the garlic tablets are readily available to the public
(B) what the diets of the two groups were during the period
(C) what effect taking the garlic tablets each day for a period of less than four months had on the levels of cholesterol and triglycerides
(D) whether large amounts of garlic are well tolerated by all patients
(E) whether the manufacturer of the garlic tablets cites the study in its advertising