This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: G.I.T, Subject name: Medicine
[{'content': 'Treatment of choice for chronic ulcerative colitis is \nSelect and explain. \nA. 5 aminosalicylic acid, B. Azathioprine, C. Metronidazole, D. Salicylates', 'role': 'user'}, {'content': 'Answer: A \nExplanation: In mild to moderate cases of ulcerative colitis, the combination of a once-daily oral and a topical 5-aminosalicylate preparation is effective. MOA of the drug is it modulate cytokine release from mucosa. Reference : Davidson, 23rd Edition, page no : 820.', 'role': 'assistant'}]