This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Circulation: Cardiac Output, Venous Return, Subject name: Physiology
Cardiac output is decreased by? 
Select and explain. 
A. Increased Heart rate, B. Decreased Heart rate, C. Increased Stroke Volume, D. None
B: Decreased Heart rate
Answer: B: Decreased Heart rate 
Explanation: ANSWER: (B) Decreased Heart rateREF: Ganong's 22nd e p. 570-571Indirect repeat from June 2011Repeat(**)Cardiac output= Stroke volume X Heart rateCardiac output is decreased by decrease in either stroke volume or heart rate or both