**Core Concept**
The ciliary movement rate of the nasal mucosa is an essential aspect of mucociliary clearance, a vital mechanism for removing pathogens, debris, and excess mucus from the respiratory tract. This process relies on the coordinated movement of cilia on the surface of epithelial cells, generating a mucous blanket that traps foreign particles.

**Why the Correct Answer is Right**
The correct answer is based on the average rate of ciliary beat frequency, which is typically around 12-15 Hz in the human nasal mucosa. This frequency is generated by the coordinated action of actin filaments and microtubules within the cilia, allowing for efficient mucociliary clearance. The ciliary beat frequency is crucial for maintaining respiratory health, as it helps to prevent infections and remove irritants from the airways.

**Why Each Wrong Option is Incorrect**
* **Option A:** 5 Hz is too low for effective mucociliary clearance, as it would result in inadequate removal of pathogens and debris.
* **Option B:** 20 Hz is too high, as it would lead to excessive clearance and potential damage to the epithelial lining.
* **Option C:** This option is not provided, making it impossible to evaluate its accuracy.

**Clinical Pearl / High-Yield Fact**
A significant decrease in ciliary beat frequency can lead to impaired mucociliary clearance, increasing the risk of respiratory infections, particularly in conditions such as primary ciliary dyskinesia.

**Correct Answer: C. 12-15 Hz**