question: Q:A 50-year-old man presents to the emergency department with chief complaints of abdominal pain, distension, and bloody diarrhea for a day. Abdominal pain was episodic in nature and limited to the left lower quadrant. It was also associated with nausea and vomiting. He also has a history of postprandial abdominal pain for several months. He had an acute myocardial infarction which was treated with thrombolytics 3 months ago. He is a chronic smoker and has been diagnosed with diabetes mellitus for 10 years. On physical examination, the patient is ill-looking with a blood pressure of 90/60 mm Hg, pulse 100/min, respiratory rate of 22/min, temperature of 38.0°C (100.5°F) with oxygen saturation of 98% in room air. The abdomen is tender on palpation and distended. Rectal examination demonstrates bright red color stool. Leukocyte count is 14,000/mm3. Other biochemical tests were within normal ranges. Abdominal X-ray did not detect pneumoperitoneum or air-fluid level. The recent use of antibiotics was denied by the patient and stool culture was negative for C. difficile. Contrast-enhanced CT scan revealed segmental colitis involving the distal transverse colon. What is the most likely cause of the patient’s symptoms?? 
  {'A': 'Hypokalemia', 'B': 'Aneurysm', 'C': 'Clostridium difficile infection', 'D': 'Embolism', 'E': 'Atherosclerosis'},