This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Environment and health, Subject name: Social & Preventive Medicine
[{'content': 'Nitrates in excess of ----mg/L may cause infantile methaemoglobinemia \nSelect and explain. \nA. 15, B. 25, C. 35, D. 45', 'role': 'user'}, {'content': "Answer: D \nExplanation: Nitrates level >50 increases the risk of infantile methaemoglobinaemia. Ref: Park's textbook of PSM 25th edition, pg 783", 'role': 'assistant'}]