This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Proteins and Amino Acids, Subject name: Biochemistry
[{'content': 'Methionine is synthesised in human body from - \nSelect and explain. \nA. Cysteine, B. Homocysteine, C. Cystine, D. Tryptophan', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Homocysteine* Homocysteine in the presence of methionine synthase and methyl B12, gets converted to methionine.", 'role': 'assistant'}]