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 characteristic feature 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: A frontal headache is usually severe and localized over affected sinus. It shows characteristic periodicity, ie. comes upon waking, gradually increases and reaches its peak by about midday and then stas subsiding. It is also called " an office headache" because of its presence during the office hours. (Ref: Textbook of Diseases of ENT, PL Dhingra, 7th edition, pg no. 214)', 'role': 'assistant'}]