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: Social & Preventive Medicine
[{'content': 'Tomatoes are rich in: \nSelect and explain. \nA. Oxalic acid, B. Citric acid, C. Acetic acid, D. Formic acid', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Citric acid', 'role': 'assistant'}]