This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Pathology
[{'content': "Which of the following is earliest sign of ulcerative colitis on double contrast barium enema (DCBE) study? \nSelect and explain. \nA. Fine Mucosal granularity, B. Loss of haustrations, C. 'Collar-button' ulcers, D. Lead pipe colon", 'role': 'user'}, {'content': 'Answer: A \nExplanation: .', 'role': 'assistant'}]