This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Radiology
[{'content': 'Which of the following investigation is used in diagnosing intestinal obstruction? \nSelect and explain. \nA. Chest X Ray, B. X ray abdomen supine, C. X ray abdomen lateral, D. Barium meal', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Obtain plain radiographs first for patients in whom small-bowel obstruction (SBO) is suspected. At least 2 views, supine or flat and upright, are required. Plain radiographs are diagnostically more accurate in cases of simple obstruction. 2 findings predictive of a higher grade or complete SBO: (1) the presence of an air-fluid differential height in the same small-bowel loop and (2) the presence of a mean level width greater than 25 mm. Dilated small-bowel loops with air-fluid levels indicate SBO, as does absent or minimal colonic gas.', 'role': 'assistant'}]