**Core Concept:** The nasopharynx is a part of the upper respiratory and digestive tract, located between the nasal cavity and the oropharynx. It is lined by specialized mucous membranes and plays a crucial role in the immune system and communication between the nasal cavity and pharynx.

**Why the Correct Answer is Right:** The correct answer, **B. Epithelial cells and pseudostratified ciliated columnar cells**, represents the primary cell types lining the nasopharynx. Epithelial cells form the majority of the nasopharyngeal lining, providing a protective barrier and facilitating absorption and secretion. Pseudostratified ciliated columnar cells are present in the respiratory epithelium and play a role in mucociliary clearance, removing foreign particles and pathogens from the respiratory tract.

**Why Each Wrong Option is Incorrect:**

A. **Nasal mucus cells**: These cells are found in the nasal cavity, not the nasopharynx.
C. **Mucous glands**: Although mucus is secreted within the nasopharynx, the specific cell types for lining are epithelial cells and pseudostratified ciliated columnar cells, not glands.
D. **Salivary gland cells**: Salivary glands are located in the mouth (parotid, submandibular, and sublingual glands) and not in the nasopharynx.

**Clinical Pearl:** Understanding the unique cell types in the nasopharynx aids in appreciating the physiological functions of the region, such as mucociliary clearance, and differentiates it from other parts of the respiratory tract or nearby structures. This knowledge is essential for interpretation of imaging studies (CT/MRI) and clinical examination findings, particularly in pediatric patients where the nasopharynx is often difficult to directly examine.