**Core Concept**
The retina is a complex neural tissue in the eye, comprising multiple layers of photoreceptor cells, bipolar cells, ganglion cells, and other neural elements. The layer in contact with the vitreous humor is crucial for maintaining the structural integrity of the eye and facilitating light transmission to the photoreceptors.

**Why the Correct Answer is Right**
The layer of the retina in contact with the vitreous humor is the **inner limiting membrane (ILM)**. The ILM is a thin, acellular layer composed of laminin, collagen, and other glycoproteins. It serves as a mechanical and biochemical interface between the retina and the vitreous humor, regulating the exchange of nutrients, waste, and ions between the two compartments. The ILM also plays a crucial role in maintaining the retinal architecture and preventing vitreoretinal traction.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the **retinal pigment epithelium (RPE)**, which is in contact with the choroid, is not in direct contact with the vitreous humor.
* **Option B:** This option is incorrect because the **internal limiting membrane (ILM)** is the correct answer, not the **internal limiting membrane** itself (a common distractor).
* **Option D:** This option is incorrect because the **ganglion cell layer**, although an important component of the retina, is not in direct contact with the vitreous humor.

**Clinical Pearl / High-Yield Fact**
The internal limiting membrane is a critical structure in vitreoretinal surgery, and its integrity is essential for preventing retinal detachment and promoting optimal visual outcomes.

**Correct Answer: A. Inner limiting membrane**