This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nose and paranasal sinuses, Subject name: ENT
[{'content': 'Periodicity is a characteritic featurw in which sinus infection: \nSelect and explain. \nA. Maxillary sinus infection, B. Frontal sinus infection, C. Sphenoid sinus infection, D. Ethmoid sinus infection', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Pain of frontal sinusitis shows characteristic periodicity,i.e comes upon walking,gradually increases and reaches its peak by midday and then stas subsiding. It is also called office headache as it is present only during office hours. Ref Dhingra 6/e p 192', 'role': 'assistant'}]