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: Surgery
[{'content': 'Necrosis of entire skin thickness and variable thickness of underlying subcutaneous tissue is: \nSelect and explain. \nA. 1st degree frostbite, B. 2nd degree frostbite, C. 3rd degree frostbite, D. 4th degree frostbite', 'role': 'user'}, {'content': 'Answer: C \nExplanation: 1st\xa0degree frostbite\xa0is hyperemia and edema of skin.\n2nd\xa0degree frostbite\xa0is hyperemia, vesicle formation and partial thickness necrosis of skin.\n3rd\xa0degree frostbite\xa0is necrosis of entire skin thickness and variable thickness of underlying subcutaneous tissue.\n\n4th\xa0degree frostbite\xa0is necrosis of entire thickness of skin and all underlying structures, leading to gangrene of the affected part.', 'role': 'assistant'}]