This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Proteins, Subject name: Social & Preventive Medicine
[{'content': 'Cereals are deficient in? \nSelect and explain. \nA. Alanine, B. Lysine, C. Methionine, D. Cysteine', 'role': 'user'}, {'content': 'Answer: B \nExplanation: ANSWER: (B) LysineREF: Park 20th edition page 542Cereals are deficient in essential amino acid lysine, maize also being deficient in tryptophan.', 'role': 'assistant'}]