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': 'Pregangrene is \nSelect and explain. \nA. Ulceration, B. Hyperaesthesia, C. Putrefaction, D. Mummification', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Pregangrene is changes in tissue which indicates that blood supply is inadequate to keep tissues alive and presents with rest pain, colour changes, oedema, hyperaesthesia.', 'role': 'assistant'}]