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
[{'content': 'Physiologically inactive form is: \nSelect and explain. \nA. Angiotensin I, B. Angiotensin II, C. Angiotensin III, D. Angiotensin IV', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Angiotensin I is <1% as potent as Ang II. Ang III and Ang II have qualitatively similar eﬀects; both stimulate aldosterone secretion with equal potency, but Ang III is only 25% and 10% as potent as\xa0Ang II in elevating blood pressure and stimulating the adrenal medulla, respectively. Angiotensin III produces the hexapeptide sometimes called angiotensin IV, which is also said to have\xa0some activity.\nThe lungs play an important role in activating angiotensin. The physiologically inactive decapeptide angiotensin I is converted\xa0to\xa0the\xa0pressor,\xa0aldosterone-stimulating\xa0octapeptide angiotensin II in the pulmonary circulation. Angiotensin\xa0III\xa0\xa0has\xa0about 40% of the pressor activity of angiotensin II, but 100% of the aldosterone-stimulating\xa0 activity. Angiotensin\xa0 III\xa0 is\xa0 simply\xa0 a\xa0 breakdown\xa0 product\xa0 with\xa0 some \u200bbiologic activity. The same is probably true of angiotensin IV, though some researchers have argued that it has unique effects in the brain.\nStructure of the amino terminal end of angiotensinogen and angiotensins\xa0I, II\xa0and III in humans.\u200b', 'role': 'assistant'}]