This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nose and PNS, Subject name: ENT
[{'content': 'Commonest cause for acute sinusitis is: \nSelect and explain. \nA. Swimming/Diving, B. Acute rhinitis, C. Nasal tumours, D. Deviated nasal septum', 'role': 'user'}, {'content': 'Answer: B \nExplanation: All of the above can cause frontal sinusitis by obstructing the frontal sinus drainage and ventilation but acute rhinitis is most common.', 'role': 'assistant'}]