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
All the following coenzymes are derivative of B-complex vitamins, Except 
Select and explain. 
A. S-adenosylmethionine, B. NAD+, C. Pyridoxal phosphate, D. Coenzyme A
A: S-adenosylmethionine
Answer: A: S-adenosylmethionine 
Explanation: .NAD+ (Niacin)Pyridoxal phosphate (Pyridoxine)Coenzyme A (pantothenate )Methionine reacts with ATP forming S-adenosylmethionine, "active methionine"Harper 30th edition pg: 308