Concerning the physiology of the coronary circulation, the following is/are true:
A.	Under circumstances of increased oxygen demand by the myocardium, O2 extraction from arterial blood can increase
B.	Coronary flow is maximal during systole
C.	Adenosine is the most important metabolic regulator of coronary blood flow
D.	Sympathetic nerve stimulation constricts coronary arteries despite the need for increased cardiac output
Answer:C
Concerning the physiology of the coronary circulation, the following is/are true:
A.	Under circumstances of increased oxygen demand by the myocardium, O2 extraction from arterial blood can increase B.	Coronary flow is maximal during systole C.	Adenosine is the most important metabolic regulator of coronary blood flow D.	Sympathetic nerve stimulation constricts coronary arteries despite the need for increased cardiac output