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: Anatomy
[{'content': 'Length of Eustachian tube? \nSelect and explain. \nA. 12 mm, B. 24mm, C. 36mm, D. 48mm', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Length of Eustachian tube is 36 mm. (reached by the age of 7 years) Lateral third (i.e. 12 mm) is bony. Medial 2/3 (i.e. 24 mm) is fibrocailaginous.', 'role': 'assistant'}]