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
Length of Eustachian tube? 
Select and explain. 
A. 12 mm, B. 24mm, C. 36mm, D. 48mm
C: 36mm
Answer: C: 36mm 
Explanation: 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.