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: Pharmacology
[{'content': 'The therapeutic effect of sulfasalazine in ulcerative colitis is exerted by : \nSelect and explain. \nA. Inhibitory action of the unabsorbed drug on the abnormal colonic flora, B. Breakdown of the drug in colon to release 5–amino-salicylic acid which suppresses inflammation locally, C. Release of sulfapyridine having antibacterial property, D. Systemic immunomodulatory action of the drug', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]