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 frostbite, 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: The localized effects of cold are frost-bite, trench foot, and immersion foot.\nTrench foot and immersion foot (wet cold) result due to prolonged exposure to severe cold (5-8° C) and dampness. Blister formation with ultceration and localized dry gangrene occurs.\nFrostbite is infarction of peripheral digits with oedema, redness and later necrosis of tissue beyond a line of inflammatory demarcation. It occurs due to exposure to greater extremes (-2.5° C) of cold. Necrosis with blister formation and gangrene occur. Skin becomes hard and black in about two weeks. The sequence of events is:-\nErythematous patches\xa0→ few hours\n\xa0Soft blisters\xa0→ 24 - 36 hours\nHard and black\xa0→ 2 weeks\nDeep up to the none\xa0→ 1 month', 'role': 'assistant'}]