This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Stroke and TIA, Subject name: Medicine
[{'content': 'Duration of T.I.A (Transient Ischemic Attacks) is less than? \nSelect and explain. \nA. 12 hours, B. 24 hours, C. 48 hours, D. 36 hours', 'role': 'user'}, {'content': 'Answer: B \nExplanation: The standard definition of TIA requires that all neurologic signs and symptoms resolve within 24 hours regardless of whether there is imaging evidence of new permanent brain injury. Stroke has occurred if the neurologic signs and symptoms last for >24 hours.', 'role': 'assistant'}]