**Core Concept**
The cornea is a transparent, avascular, and stratified epithelial structure that forms the anterior portion of the eye. The cornea's unique structure and function require specialized cell types and tissues for its maintenance.

**Why the Correct Answer is Right**
The cornea is lined by a stratified epithelium composed of five to six layers of epithelial cells. This stratified epithelium is essential for maintaining the cornea's transparency and preventing water loss. The basal layer of the epithelium is in contact with the Bowman's layer, a dense collagenous layer that provides additional structural support to the cornea.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the conjunctiva, a mucous membrane that covers the sclera, is not the primary lining of the cornea.
**Option B:** This option is incorrect because the uvea, the pigmented layer of the eye, is not in direct contact with the cornea.
**Option C:** This option is incorrect because the retina, the innermost layer of the eye, is not a part of the cornea.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the cornea lacks blood vessels, which makes it vulnerable to ischemia and subsequent corneal ulceration or perforation. This is a critical consideration in the management of corneal injuries or diseases.

**Correct Answer:** D. Stratified epithelium. Stratified epithelium lines the cornea.