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
Volume determining preload is: 
Select and explain. 
A. End diastolic volume of ventricles, B. Endo systolic volume, C. Volume of blood in aoa, D. Ventricular ejection volume
A: End diastolic volume of ventricles
Answer: A: End diastolic volume of ventricles 
Explanation: A i.e End diastolic volume of ventricles According to frank-starling law, the length of muscle fibers (extent of the pre-load) is propoionate to the end diastolic volumeQ