This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Ear, Subject name: ENT
[{'content': 'Length of external auditory canal is? \nSelect and explain. \nA. 12 mm, B. 24 mm, C. 36 mm, D. 48 mm', 'role': 'user'}, {'content': "Answer: B \nExplanation: ANSWER: (B) 24 mmREF: Dhingra 4th edition page 400'External auditory canal of an adult is 24 mm in length. Outer one-third (8 mm) is cartilaginous and inner two thirds (16 mm) are bony'1", 'role': 'assistant'}]