**Core Concept**
The question is testing the student's knowledge of amino acid chirality and optical activity. Amino acids are organic compounds that contain both a carboxyl (-COOH) and an amino (-NH2) group, and they can exist in different stereoisomeric forms, known as enantiomers or optical isomers. The optical activity of an amino acid is determined by the presence of a chiral center, usually a carbon atom bonded to four different groups.

**Why the Correct Answer is Right**
The correct answer is an amino acid that lacks a chiral center, making it optically inactive. This occurs when two of the four groups attached to the chiral carbon are identical, resulting in a loss of optical activity. One such amino acid is **Cycloleucine**, a cyclic derivative of the amino acid leucine, where the chiral center is eliminated by the formation of a ring structure.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not provided, so no explanation is possible.
* **Option B:** This option is also not provided, so no explanation is possible.
* **Option C:** This option is not provided, so no explanation is possible.
* **Option D:** This option is not provided, so no explanation is possible.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that amino acids with a chiral center are optically active, while those without a chiral center are optically inactive. This distinction is crucial in understanding the stereochemistry of amino acids and their interactions with enzymes and other molecules.

**Correct Answer:** C. Cycloleucine