The answer is b) mandibular.
Paranasal sinuses are air-filled spaces within the bones of the skull that are connected to the nasal cavity. The main paranasal sinuses include the maxillary, frontal, ethmoid, and sphenoid sinuses. Each of these is located in a specific area around the nose and plays a role in reducing the weight of the skull, producing mucus, and filtering the air we breathe.
In this context, the maxillary sinus is found in the cheek area; the frontal sinus is located in the forehead region; and the ethmoid sinuses are situated between the eyes. On the other hand, the mandibular area refers to the lower jawbone, which does not have any sinuses associated with it that are categorized as paranasal.
Thus, the correct answer is that the mandibular is not a paranasal sinus.