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
Melatonin is derived from ? 
Select and explain. 
A. Tyrosine, B. Tryptophan, C. Glutathione, D. None
B: Tryptophan
Answer: B: Tryptophan 
Explanation: Ans. is 'b' i.e., Tryptophan