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: Forensic Medicine
[{'content': 'In frost bite, skin becomes hard black in about : \nSelect and explain. \nA. 3 days, B. 7 days, C. 2 weeks, D. 4-6 weeks', 'role': 'user'}, {'content': 'Answer: C \nExplanation: C i.e. 2 weeks Trench (immersion) foot results from prolonged exposure to severe cold (5 -8degc) of dampness. Frost bite occurs d/t exposure to greater extremes of cold (-2.5degc), develops more rapidly, & may affect other pas such as nose, ears. Skin becomes hard & black in 2 weeksQ (after initial blanching & paleness erythema & edema bisters).', 'role': 'assistant'}]