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
Myocardial oxygen demand depend upon all except: 
Select and explain. 
A. Preload, B. Afterload, C. Intramyocardial tension, D. Blood Hb concentration
D: Blood Hb concentration
Answer: D: Blood Hb concentration 
Explanation: Hb concentration determines the O2 supply to myocardium, not myocardial O2 demand.