Which of the following describes a cardiovascular effect of smoking?

• A. Smoking increases heart rate and blood pressure.
• B. The chemicals nicotine and carbon monoxide damage artery linings, decrease oxygen capacity, and increase blood viscosity.
• C. Smoking reduces risk of stroke.
• D. It improves oxygen delivery to tissues.

Answer: (B)

Smoking harms the cardiovascular system through multiple interacting mechanisms. The chemicals in tobacco damage the lining of arteries, promoting endothelial injury that starts or accelerates atherosclerosis and makes vessels more prone to constriction and plaque formation. At the same time, nicotine and carbon monoxide create functional stresses: nicotine stimulates the sympathetic system, raising heart rate and blood pressure, while carbon monoxide binds hemoglobin to form carboxyhemoglobin, reducing the blood’s oxygen-carrying capacity. Smoking also increases blood viscosity, partly from higher hematocrit and platelet activity, which makes the heart work harder and raises the risk of clots.

This combination—endothelial damage, reduced oxygen delivery, and increased viscosity—best captures the cardiovascular harms of smoking in a single statement, so it’s the most complete description of how smoking affects the heart and vessels. The other ideas are true to some extent (like acutely higher heart rate and blood pressure), but they don’t convey the full range of harmful effects, and one choice even states an effect that isn’t true (that smoking reduces stroke risk or improves oxygen delivery).