<span>When a person smokes a cigarette, the body responds immediately to the chemical nicotine in the smoke. Nicotine causes a short-term increase in blood pressure, heart rate, and the flow of blood from the heart. It also causes the arteries to narrow. Carbon monoxide reduces the amount of oxygen the blood can carry. This, combined with the effects produced by nicotine, creates an imbalance in the demand for oxygen by the cells and the amount of oxygen the blood is able to supply.
So the answer is D. increased heart rate</span>
