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': 'Half of the clot retraction is completed by? \nSelect and explain. \nA. 24 hrs, B. Within 2 hrs, C. Within 15 minutes, D. Within 1 hour', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]