**Core Concept**
The definitive color of the iris is determined by the amount and distribution of pigment, specifically melanin, in the iris stroma and epithelium. The interaction between light and melanin in the iris stroma scatters light and gives the iris its characteristic color.

**Why the Correct Answer is Right**
The correct answer is related to the interaction between light and melanin in the iris stroma. When light enters the eye, it encounters melanin in the iris stroma, which scatters the shorter wavelengths of light (blue and violet) more than the longer wavelengths (red and yellow). This scattering effect gives the iris its characteristic color. The amount and distribution of melanin in the iris stroma determine the intensity and hue of the iris color.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not mentioned in the context of iris color.
* **Option B:** This option is not directly related to the definitive color of the iris.
* **Option C:** This option is incorrect as it does not accurately describe the mechanism of iris color determination.

**Clinical Pearl / High-Yield Fact**
The amount and distribution of melanin in the iris stroma can vary greatly between individuals, resulting in a wide range of iris colors, from blue to brown. The interaction between light and melanin in the iris stroma is the key factor in determining the definitive color of the iris.

**Correct Answer:** C.