**Core Concept**
The middle meatus is a critical anatomical area within the nasal cavity, serving as a passage for several important structures. It is a narrow airway that receives drainage from various paranasal sinuses, playing a vital role in the respiratory and olfactory functions of the nasal passages.

**Why the Correct Answer is Right**
The posterior ethmoid sinuses drain into the superior meatus, not the middle meatus. This is because the posterior ethmoid sinuses are located more posteriorly and superiorly within the ethmoid labyrinth, and their drainage pathway diverges from the middle meatus. The middle meatus receives drainage from the anterior ethmoid sinuses, the frontal air sinus, and the maxillary sinus through the semilunar hiatus.

**Why Each Wrong Option is Incorrect**
**Option A:** The middle ethmoidal air sinuses, also known as the anterior ethmoid sinuses, drain into the middle meatus through the infundibulum. This is a critical pathway for the drainage of these sinuses.
**Option B:** The maxillary sinus drains into the middle meatus through the semilunar hiatus, making it a correct option.
**Option D:** The frontal air sinus also drains into the middle meatus through the semilunar hiatus, similar to the maxillary sinus.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that the drainage pathways of the paranasal sinuses can vary, but the middle meatus is a key location for the drainage of several sinuses, including the anterior ethmoid sinuses, frontal air sinus, and maxillary sinus. Understanding these drainage pathways is crucial for the diagnosis and management of sinus-related disorders.

**✓ Correct Answer: C. Posterior ethmoid sinuses**