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
Shortest length of middle ear: 
Select and explain. 
A. 2 mm, B. 4 mm, C. 6 mm, D. 1 cm
A: 2 mm
Answer: A: 2 mm 
Explanation: Ans. (a) 2 mmRef: Dhingra's ENT 6th ed./ 9-10* Length of middle ear canal:# Epitympanum- 6mm# Mesotympanum- 2mm# Hypotympanum- 4mm* Shortest distance between tympanic membrane to promontory: 2mm.