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: Unknown
[{'content': 'Hyperacute rejection occurs within: \nSelect and explain. \nA. 12 hours, B. 2 weeks, C. 1 month, D. 3 months', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ref. Robbins Pathology. 9th edition. Page. 233\n\xa0\nHyperacute Rejection\n\nThis form of rejection occurs within minutes or hours after transplantation.\nA hyperacutely rejecting kidney rapidly becomes cyanotic, mottled, and flaccid, and may excrete a mere few drops of bloody urine.\nImmunoglobulin and complement are deposited in the vessel wall, causing endothelial injury and fibrin-platelet thrombi\nGlomeruli undergo thrombotic occlusion of the capillaries, and fibrinoid necrosis occurs in arterial walls.\nThe kidney cortex then under- goes outright necrosis (infarction), and such nonfunctioning kidneys have to be removed.', 'role': 'assistant'}]