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: Radiology
[{'content': 'Amount of radiation which causes injury to CVS or CNS: \nSelect and explain. \nA. 7 Gy, B. 15 Gy, C. 30 Gy, D. 50 Gy', 'role': 'user'}, {'content': "Answer: D \nExplanation: Exposures greater than 50 Gy usually cause death in 1 to 2 days.\xa0\nThe few humans who have been exposed at this level showed collapse\xa0of\xa0the\xa0circulatory\xa0system\xa0with\xa0a\xa0precipitous\xa0fall\xa0in\xa0blood pressure in the hours preceding death.\xa0\nAutopsy revealed necrosis of\xa0cardiac\xa0muscle. Victims\xa0also\xa0may\xa0present\xa0with\xa0intermittent stupor, incoordination, disorientation\xa0and convulsions, suggestive of extensive damage to the nervous system.\xa0\n\xa0\nWhite and Pharoah's Oral\xa0Radiology Principles and Interpretation 7th edition", 'role': 'assistant'}]