**Core Concept**
The paranasal sinuses are air-filled cavities located within the bones of the face, including the frontal, maxillary, ethmoid, and sphenoid sinuses. These sinuses are involved in the production of mucus and play a role in the resonance of sound.

**Why the Correct Answer is Right**
The frontal sinus is a paranasal sinus located in the frontal bone, above the eyebrows. The maxillary sinus is the largest paranasal sinus, located in the maxilla bone, and is responsible for the resonance of the nasal voice. The ethmoid sinus is composed of multiple small air cells within the ethmoid bone, between the nasal cavity and the orbits. The sphenoid sinus is located within the sphenoid bone, behind the nasal cavity.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not provided, but if you're looking for a paranasal sinus that is not listed, the lacrimal sac is not a paranasal sinus. It is a small, tear-producing gland located in the lacrimal bone, near the medial canthus of the eye. It is involved in the production of tears and is not an air-filled cavity.

**Clinical Pearl / High-Yield Fact**
The paranasal sinuses are involved in the resonance of sound, particularly the nasal voice, which is why patients with chronic sinusitis may experience changes in their voice.

**Correct Answer:** A. Lacrimal sac is not a paranasal sinus.