Numbers Game: Pack Attack

After controlling for confounding variables, the HDL (protective cholesterol) levels of women who smoke a pack of cigarettes a day are, on average, _________ lower than those of their non-smoking counterparts.

Source: The National Heart, Lung, and Blood Institute Family Heart Study

a) 25
b) 8
c) 17
d) 10

Leave your guess in the "comments" section and come back on Friday for the answer.