**Core Concept**
The ethmoidal sinuses are a group of small air cells within the ethmoid bone, which is located between the nose and the eye. The paranasal sinuses are connected to the nasal cavity through various ostia, and understanding their drainage pathways is crucial for diagnosing and treating sinusitis.

**Why the Correct Answer is Right**
The ethmoidal sinuses open into the middle meatus of the nasal cavity. This is due to the presence of the middle nasal conchae, which is a scroll-like structure that separates the middle meatus from the superior and inferior meatus. The middle meatus receives drainage from the anterior ethmoidal cells, the frontal sinus, and the maxillary sinus's anterior ethmoidal cells. The ethmoidal bulla, a bony structure within the middle meatus, also helps to direct the drainage from the anterior ethmoidal cells into the infundibulum of the frontal sinus.

**Why Each Wrong Option is Incorrect**
**Option A:** The superior meatus is primarily involved with the drainage of the posterior ethmoidal cells and the sphenoid sinus. This is not the primary drainage pathway for the ethmoidal sinuses.
**Option B:** The inferior meatus is primarily involved with the nasolacrimal duct. This duct carries tears from the eye into the nasal cavity, but it is not a primary drainage pathway for the ethmoidal sinuses.
**Option C:** The nasopharynx is the posterior part of the nasal cavity that leads to the oropharynx. While it is a part of the nasal cavity, it is not a primary drainage pathway for the ethmoidal sinuses.

**Clinical Pearl / High-Yield Fact**
The paranasal sinuses are connected to the nasal cavity through various ostia, and understanding their drainage pathways is crucial for diagnosing and treating sinusitis. The presence of a high fever, facial pain, and nasal congestion may indicate acute sinusitis, which requires prompt medical attention.

**Correct Answer:** C.