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
The therapeutic effect of sulfasalazine in ulcerative colitis is exerted by : 
Select and explain. 
A. 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
B: Breakdown of the drug in colon to release 5–amino-salicylic acid which suppresses inflammation locally
Answer: B: Breakdown of the drug in colon to release 5–amino-salicylic acid which suppresses inflammation locally 
Explanation: None