Question

which is a benefit of quitting smoking?
decreased allergic reactions
increased risk of high blood pressure
increased asthma problems
decreased risk of blood clot formation

Explanation:

Smoking is a risk - factor for blood clot formation. Quitting reduces this risk. Decreased allergic reactions are not directly related to quitting smoking. Increased risk of high blood pressure and asthma problems are negative effects of smoking, not benefits of quitting.

Answer:

decreased risk of blood clot formation