This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Physiology
Coronary blood flow, true is 
Select and explain. 
A. 250ml/min, B. Maximum during systole, C. Adenosine decreases it, D. More than skin
B: Maximum during systole
Answer: B: Maximum during systole 
Explanation: Coronary flow at rest in humans is about 250 mL/min (5% of the cardiac output).Consequently, flow occurs in the aeries supplying the subendocardial poion of the left ventricle only during diastoleAdenosine cause coronary vasodilation and decrease flowCutaneous blood flow is about 10-15 mL/min/cutaneous tissue whereas in hea it is 70mL/100g tissue/minRef: Ganong's Review of Medical Physiology Twenty-Third Edition Page No:578