A healthy 35-year-old male undergoes a physiological stress test. Which of the following best describes the primary mechanism by which an increase in end-diastolic volume leads to an increase in stroke volume?

✓ Correct Answer: Option B

The Frank-Starling mechanism states that increased venous return leads to increased ventricular filling (end-diastolic volume), stretching cardiac muscle fibers to a more optimal length for actin-myosin cross-bridge formation, thus increasing contractile force and stroke volume.