This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Non communicable diseases, Subject name: Social & Preventive Medicine
[{'content': 'BMI cut off for obesity is - \nSelect and explain. \nA. 28, B. 30, C. 32, D. 40', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ref-Park&;s textbook of Preventive and Social Medicine 24th edition. .', 'role': 'assistant'}]