system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
Sinus not present at birth is:
assistant
The correct answer is  (c) Frontal(Ref. Cummings, 6th ed., 2874; Scott Brown, 8th ed., Vol 2, page 262)This is the last sinus to develop. It is not present at birth.