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
All of the following are topically used sulphonamides except - 
Select and explain. 
A. Sulphacetamide, B. Sulphadiazine, C. Silver sulphadiazine, D. Mafenide
B: Sulphadiazine
Answer: B: Sulphadiazine 
Explanation: Ans is 'b' i.e., Sulphadiazine Topical Sulfonamides - Sulfacetamide sodium, Mafenide, silver sulfadiazine.