Which of the following typically increases during moderate exercise due to increased demand?

During moderate exercise, heart rate typically increases to meet the elevated demands of the body. As physical activity intensifies, the muscles require more oxygen and nutrients to sustain their activity, which leads to an increased metabolic rate. To accommodate this increased demand, the cardiovascular system responds by increasing the heart's output. This is achieved through an increase in heart rate, which is controlled by the autonomic nervous system.

While blood flow to the stomach generally decreases during exercise as prioritization shifts towards working muscles, pulmonary resistance tends to decrease to allow for more efficient gas exchange. Venous return, although it may increase due to muscle pump activity during exercise, is not directly driven by the demand but rather supported through various mechanisms. The heart rate increase is a fundamental and critical response to ensure adequate oxygen delivery to the active tissues, making it the most appropriate choice.