question: Q:A 67-year-old man presents to the physician with profuse watery diarrhea along with fever and crampy abdominal pain. He has been taking an antibiotic course of cefixime for about a week to treat a respiratory tract infection. At the doctor’s office, his pulse is 112/min, the blood pressure is 100/66 mm Hg, the respirations are 22/min, and the temperature is 38.9°C (102.0°F). His oral mucosa appears dry and his abdomen is soft with vague diffuse tenderness. A digital rectal examination is normal. Laboratory studies show:
  Hemoglobin 11.1 g/dL
  Hematocrit 33%
  Total leucocyte count 16,000/mm3
  Serum lactate 0.9 mmol/L
  Serum creatinine 1.1 mg/dL
  What is most likely to confirm the diagnosis?? 
  {'A': 'Identification of C. difficile toxin in stool', 'B': 'Stool culture', 'C': 'Colonoscopy', 'D': 'Abdominal X-ray', 'E': 'CT scan of the abdomen'},