The respiratory tract is lined internally with a .................. epithelium.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks what type of epithelium lines the respiratory tract internally.

2. **Definition of Epithelium**: Epithelium is a type of tissue made up of tightly packed cells that cover surfaces or line cavities in the body.

3. **Function of the Respiratory Tract**: The respiratory tract serves as a passage for air to enter the lungs, where gas exchange occurs. It also conditions the air by filtering, warming, and moistening it.

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