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
Surface area of tympanic membrance 
Select and explain. 
A. 55mm2, B. 70mm2, C. 80mm2, D. 90mm2
D: 90mm2
Answer: D: 90mm2 
Explanation: The surface area of tympanic membrane is 90 mm2. Only 55 mm2 is functional. Ref: PL Dhingra 6th edition of Ear, Nose and Throat; pg no 14