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: ENT
[{'content': 'A 2 years male boy presenting with sudden severe dyspnoea, most common cause is - \nSelect and explain. \nA. Foreign body, B. Bronchiolitis, C. Asthmatic Attack, D. None', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]