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 is a less useful diagnostic procedure in a case of acute haematemesis? \nSelect and explain. \nA. Barium meal, B. Endoscopy, C. Gastric content aspiration, D. Angiography', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. Barium meal', 'role': 'assistant'}]