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
Cardiac output is a measure of: 
Select and explain. 
A. Peripheral resistance X tissue fluid, B. Peripheral resistance X cardiac rate, C. Blood pressure X cardiac rate, D. Heart rate X blood volume
D: Heart rate X blood volume
Answer: D: Heart rate X blood volume 
Explanation: None