**Core Concept**
The refractive index of the cornea is a critical parameter in ophthalmology, determining the eye's ability to focus light. The cornea's refractive index is higher than that of the aqueous humor, allowing it to contribute significantly to the eye's total refractive power.

**Why the Correct Answer is Right**
The correct answer is 1.376, which is the average refractive index of the human cornea. This value is essential for calculating the eye's refractive power and is used in ophthalmic calculations, such as those for intraocular lens power and corneal transplantation. The cornea's refractive index is influenced by its protein and water content, with a higher protein content contributing to a higher refractive index.

**Why Each Wrong Option is Incorrect**
* **Option A:** This value is too low and does not accurately represent the cornea's refractive index.
* **Option B:** This value is too high and is more representative of the lens's refractive index.
* **Option D:** This value is incorrect and does not accurately represent the cornea's refractive index.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the cornea's refractive index is a critical factor in ophthalmic calculations, and small changes in this value can significantly impact the accuracy of these calculations. For example, an error in corneal refractive index can lead to incorrect intraocular lens power, resulting in suboptimal visual outcomes.

**Correct Answer: D. 1.376**