The answer is A. Quit smoking. Smoking affects the lungs terribly which can greatly affect your heart since they are both part of the cardiovascular system.
EDIT: To further explain, smoking affects your respiratory system (lungs, bronchioles, etc.) however the cardiovascular system depends on the respiratory system. Overall they both keep blood flowing through the arteries of the body. Smoking damages the lining of your arteries, leading to a build up of fatty material which narrows the artery.
