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': 'In halo sign seen in csf rhinorrhea: \nSelect and explain. \nA. Blood is encircled with csf., B. CSF is encircled with blood., C. Both are mixed no demarcation., D. None of the above.', 'role': 'user'}, {'content': 'Answer: A \nExplanation: CSF rhinorrhea seen in\nLefort 2&3\nNaso orbital ethmoid fracture.\nCribiform plate fracture.\nFrontal sinus fracture.\nSphenoidal sinus fracture', 'role': 'assistant'}]