Which of the following factors could lower resting heart rate?

Regular cardiovascular exercise is known to lower resting heart rate primarily due to the adaptations that occur in the cardiovascular system as a result of consistent training. Engaging in aerobic activities like running, swimming, or cycling strengthens the heart muscle, enabling it to pump a greater volume of blood with each beat. This efficiency allows the heart to beat fewer times per minute when at rest, which is reflected in a lower resting heart rate. Additionally, regular exercise enhances overall cardiovascular health and can promote a more robust autonomic nervous system, further supporting a lower resting heart rate.

In contrast, high caffeine consumption typically stimulates the heart and can lead to an increased resting heart rate. Stress and anxiety activate the body's fight-or-flight response, leading to elevated heart rates as well. Overeating can also result in an increased heart rate as the body works harder to digest the food. Therefore, regular cardiovascular exercise is the most effective factor in lowering resting heart rate.