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
[{'content': 'Which of the following is the precursor of adrenaline and noradrenaline? \nSelect and explain. \nA. Phenylalanine, B. Tyrosine, C. Tryptophan, D. None of the above', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Tyrosine is the contributing amino acid for the formation of thyroxine, tri-iodothyronine, epinephrine, norepinephrine, dopamine and melanin', 'role': 'assistant'}]