This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of protein and amino acid, Subject name: Biochemistry
[{'content': 'Cysteine is formed from \nSelect and explain. \nA. Methionine and serine, B. Methionine and glycine, C. Alanine and glycine, D. Serine and glycine', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Serin+Homocystein ------->Cysteine+Homoserin.Homocystein is synthesized from Methionine.Ref: DM Vasudevan - Textbook of Biochemistry, 7th edition, page no: 217, Fig no 16.15', 'role': 'assistant'}]