This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
Which of the following factor is determined by preload? 
Select and explain. 
A. End systolic volume, B. End diastolic volume, C. Peripheral resistance, D. Stroke volume
B: End diastolic volume
Answer: B: End diastolic volume 
Explanation: Preload is the initial stretching of the cardiac myocytes prior to contraction; therefore, it is related to the sarcomere length at the end of diastole. Sarcomere length cannot be determined in the intact hea so indirect indices of preload, such as ventricular end-diastolic volume or pressure, must be used. Ref: Cardiovascular Physiology Concepts By Richard E. Klabunde, 2005, Page 69; Guyton's physiology 22nd edition, Page 111.