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
Commonest cause for acute sinusitis is: 
Select and explain. 
A. Swimming/Diving, B. Acute rhinitis, C. Nasal tumours, D. Deviated nasal septum
B: Acute rhinitis
Answer: B: Acute rhinitis 
Explanation: All of the above can cause frontal sinusitis by obstructing the frontal sinus drainage and ventilation but acute rhinitis is most common.