**Core Concept**
The ciliary body is a critical structure in the eye, responsible for lens accommodation and aqueous humor production. The non-pigmented epithelium of the ciliary body plays a key role in aqueous humor production and is in close proximity to the lens.

**Why the Correct Answer is Right**
The non-pigmented epithelium of the ciliary body is the forward continuation of the retinal pigment epithelium (RPE). This is because both layers are involved in the production and maintenance of the blood-retina barrier. The RPE produces melanin, which protects the retina from excessive light, while the non-pigmented epithelium of the ciliary body produces aqueous humor, which nourishes the lens. The two layers are continuous, with the RPE transitioning into the non-pigmented epithelium of the ciliary body at the ora serrata.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the non-pigmented epithelium of the ciliary body is not a continuation of the choroid, which is a layer of blood vessels between the sclera and retina.

**Option B:** This option is incorrect because the non-pigmented epithelium of the ciliary body is not a continuation of the iris, which is a pigmented structure that regulates light entry into the eye.

**Option C:** This option is incorrect because the non-pigmented epithelium of the ciliary body is not a continuation of the lens epithelium, which is a single layer of cells on the anterior surface of the lens.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the non-pigmented epithelium of the ciliary body is involved in aqueous humor production, which can be affected in conditions such as glaucoma.

**Correct Answer: C. The retina.**