**Core Concept**
Two same-charged proteins can be separated by exploiting differences in their physical properties, such as size, shape, and hydrophobicity. This principle is crucial in various biochemical and biophysical techniques used in research and clinical diagnostics.

**Why the Correct Answer is Right**
The correct technique for separating same-charged proteins is size-exclusion chromatography (SEC), also known as gel filtration. In SEC, proteins are separated based on their size, with larger molecules being excluded from the smaller pores within the chromatographic matrix. This allows for the separation of proteins with the same charge but different molecular weights. The smaller pores in the matrix allow smaller molecules to pass through, while larger molecules are retained and elute later, resulting in a separation of the proteins based on their size.

**Why Each Wrong Option is Incorrect**
**Option A:** Ion exchange chromatography (IEC) separates proteins based on their charge, which is not applicable for same-charged proteins. IEC uses charged functional groups on the chromatographic matrix to interact with oppositely charged proteins, allowing for their separation.
**Option B:** Affinity chromatography separates proteins based on specific interactions between the protein and a ligand, which is not relevant for separating same-charged proteins by size.
**Option C:** Electrophoresis separates proteins based on their charge and size, but it is not the most suitable technique for separating same-charged proteins, as it relies on the protein's charge for separation.

**Clinical Pearl / High-Yield Fact**
Size-exclusion chromatography is a versatile technique used in various applications, including protein purification, analysis of protein size and shape, and characterization of protein-protein interactions.

**Correct Answer:** C.