Final answer:
There are four paranasal sinuses that drain into the nasal passageways: the frontal sinus, maxillary sinus, sphenoidal sinus, and ethmoidal sinus. Therefore, the correct answer is C. 4.
Step-by-step explanation:
The question asks how many paranasal sinuses drain into the nasal passageways in human anatomy. There are four main paranasal sinuses that fulfill this function:
the frontal sinus, located in the frontal bone above the eyebrows; the maxillary sinus, the largest of the sinuses, located in the maxillary bones below the orbits; the sphenoidal sinus, positioned in the sphenoid bone's body, beneath the sella turcica; and the ethmoidal sinus (or ethmoid air cells), multiple small spaces found within the ethmoid bone, between the upper nasal cavity and the medial orbit. Hence, the correct answer to this question is C. 4, since all four of these sinuses drain into the nasal passageways.