<prompt> Pack year means10 cigarettes per day for 1 year20 cigarettes per day for 1 year40 cigarettes per day for 1 year50 cigarettes per day for 1 year  <response>: B 20 cigarettes per day for 1 year A pack-year is a quantification of cigarette smoking. 1 pack-year is equal to smoking 20 cigarettes 1 pack per day for 1 year, or 40 cigarettes per day for half a year, and so on. Number of pack-years packs smoked per day years as a smoker. 