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: ENT
Length of the external auditory canal is 
Select and explain. 
A. 20 mm, B. 22 mm, C. 24 mm, D. 15 mm
C: 24 mm
Answer: C: 24 mm 
Explanation: EXTERNAL AUDITORY CANAL

It starts at the external auditory meatus and ends at the tympanic membrane, where a bony structure (bony outer attic wall at tympanic membrane, where ECA ends) projects, called scutum.
It is almost S-shaped curved canal of about 24 mm length.
It has - outer cartilaginous part (2/3rd) and - inner bony part (l/3rd).
It is directed upwards, backward and medially in the outer part and downwards, forwards and medially in the inner part.
The periosteum is very firmly adherent in EAC and hence even a minor infection like a furuncle is extremely painful.