This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Heart, Circulation, and Blood, Subject name: Physiology
[{'content': 'Volume determining preload is \nSelect and explain. \nA. End diastolic volume of ventricles, B. End systolic volume, C. Volume of blood in aorta, D. Ventricular ejection volume', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. (a) End diastolic volume of ventriclesRef: Ganong, 25th ed/p.544Preload is End diastolic volume of ventriclesAfterload is the aortic pressure', 'role': 'assistant'}]