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
Longest acting sulphonamide is – 
Select and explain. 
A. Sulfadiazine, B. Sulfadoxine, C. Sulfamethoxazole, D. Sulfamethiazole
B: Sulfadoxine
Answer: B: Sulfadoxine 
Explanation: None