This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: vitamins, Subject name: Biochemistry
Which of the following vitamins contain sulfur in its structure? 
Select and explain. 
A. Thiamine, B. Riboflavin, C. Folic acid, D. Niacin
A: Thiamine
Answer: A: Thiamine 
Explanation: Thiamine contains Sulphur in its structure. Structure of Thiamine: Thiamine contains a substituted pyrimidine ring connected to a substituted thiazole ring by means of methylene bridge. The vitamin is then conveed to its active co-enzyme form by addition of two phosphate groups, with the help of ATP (Fig. 34.1). It is catalyzed by thiamine pyrophosphotransferase. Reference: Vasudevan Textbook of Biochemistry pg no.391