<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:An 87-year-old male nursing home resident is currently undergoing antibiotic therapy for the treatment of a decubitus ulcer. One week into the treatment course, he experiences several episodes of watery diarrhea. Subsequent sigmoidoscopy demonstrates the presence of diffuse yellow plaques on the mucosa of the sigmoid colon. Which of the following is the best choice of treatment for this patient?? A: Oral morphine, B: Intravenous gentamicin, C: Oral metronidazole, D: Oral trimethoprimsulfamethoxazole, E: Intravenous vancomycin,  <response>: This is a clinical vignette about an elderly male nursing home resident who is being treated with antibiotics for a decubitus ulcer. He develops diarrhea during the antibiotic course. Sigmoidoscopy shows yellow plaques in his colon, which indicates pseudomembranous colitis likely due to Clostridium difficile infection. The best treatment choice for C. difficile colitis is oral metronidazole. The other options are not appropriate treatments.C: Oral metronidazole 