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: Biochemistry
Which of the following vitamins is not involved in TCA cycle? 
Select and explain. 
A. Riboflavin, B. Thiamine, C. Niacin, D. Pyridoxine
D: Pyridoxine
Answer: D: Pyridoxine 
Explanation: Vitamins in TCA cycle are :

Thiamine (B1)
Riboflavin (B2)
Niacian (B3)
Pantothenic acid (B5)