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
The causative agent for virulent external ear infection in a diabetic elderly is mostly by 
Select and explain. 
A. Staphylococcus, B. Streptococcus, C. Pseudomonas, D. Hemophilus influenzae
C: Pseudomonas
Answer: C: Pseudomonas 
Explanation: Pseudomonas aeruginosa is the agent which is responsible for virulent external ear infection in diabetics, mainly Necrotizing otitis externa. (Ref: Textbook of diseases of ENT, PL Dhingra, 7th edition, pg no. 55)