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
Most potent vasopresser is: 
Select and explain. 
A. Angiotensin II, B. Renin., C. Aldosterone., D. Cortisole
A: Angiotensin II
Answer: A: Angiotensin II 
Explanation: Ganong 22 –456
Angiotensin I appears to function solely as the precursor of angiotensin II does not have any other established action. Angiotensin II- previously called hypertension or angiotonin- produces arteriolar constriction and a rise in systolic and diastolic blood pressure. It is one of the most potent vasoconstrictors known, being four to eight times as active as norepinephrine.