<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:An 81-year-old man comes to the emergency department with severe left ear pain and drainage for 3 days. He has a history of poorly-controlled type 2 diabetes mellitus. He appears uncomfortable. Physical examination of the ear shows marked periauricular erythema, exquisite tenderness on palpation, and granulation tissue in the external auditory canal. The most likely causal pathogen produces an exotoxin that acts by a mechanism most similar to a toxin produced by which of the following organisms?? A: Corynebacterium diphtheriae, B: Bordetella pertussis, C: Shigella dysenteriae, D: Staphylococcus aureus, E: Bacillus anthracis,  <response>: This is a medical question asking about the most likely causal pathogen and exotoxin mechanism in an elderly man with severe ear pain, drainage, and physical exam findings concerning for otitis externa with cellulitis. The key clues are the poorly controlled diabetes, granulation tissue, and exotoxin production, which point towards Pseudomonas aeruginosa infection. Pseudomonas produces exotoxin A, which inhibits protein synthesis by ADP-ribosylation of elongation factor 2, similar to diphtheria toxin produced by Corynebacterium diphtheriae.A: Corynebacterium diphtheriae 