**Core Concept**
The somatic non-stochastic effect of radiation refers to the deterministic effects of ionizing radiation on the human body, which occur at a certain threshold dose and increase in severity with the dose received. These effects are typically seen in tissues with a high rate of cell division, such as bone marrow and the gastrointestinal tract.

**Why the Correct Answer is Right**
The correct effect of radiation is **Radiation Dermatitis**. This occurs when the dose of radiation exceeds the threshold of 2 Gy, leading to damage to the skin's epidermal cells, causing redness, dryness, and peeling. The severity of radiation dermatitis increases with the dose received, making it a classic example of a somatic non-stochastic effect.

**Why Each Wrong Option is Incorrect**
**Option A:** Bone Marrow Failure - This is a correct effect of radiation, but it is a stochastic effect, not a non-stochastic effect.
**Option B:** Cataract Formation - This is a correct effect of radiation, but it is a stochastic effect, not a non-stochastic effect.
**Option C:** Sterility - This is a correct effect of radiation, but it is a stochastic effect, not a non-stochastic effect.

**Clinical Pearl / High-Yield Fact**
Remember the "RED" rule for non-stochastic effects: "Radiation Dermatitis" occurs at doses > 2 Gy, and the severity increases with dose. This is in contrast to stochastic effects, which occur at any dose and have a threshold of zero.

**Correct Answer:** C. Radiation Dermatitis