This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.N.S., Subject name: Medicine
[{'content': 'Cut off for TIA definition: \nSelect and explain. \nA. 12 hours, B. 24 hours, C. 48 hours, D. 36 hours', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. B. 24 hoursThe 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'}]