**Core Concept**
Electrophoresis is a laboratory technique used to separate and identify proteins based on their charge, size, and shape. This method is crucial in biochemistry, molecular biology, and clinical diagnostics for analyzing proteins in various samples.

**Why the Correct Answer is Right**
The correct method to differentiate proteins is by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). SDS-PAGE separates proteins based on their molecular weight, as SDS binds to the proteins, giving them a uniform negative charge. This uniform charge allows the proteins to migrate through the gel based on their size, with smaller proteins moving faster. The separated proteins are then visualized using stains such as Coomassie Blue or silver nitrate.

**Why Each Wrong Option is Incorrect**
**Option A:** Isotachophoresis is a technique used to separate ions based on their mobility, not proteins.
**Option B:** Capillary electrophoresis is a technique used to separate and analyze small molecules, not proteins.
**Option C:** Chromatography is a broad term that encompasses various techniques for separating and purifying substances, but it is not specific to proteins.

**Clinical Pearl / High-Yield Fact**
SDS-PAGE is a fundamental technique in biochemistry and molecular biology, and its results are often used to diagnose genetic disorders, identify protein modifications, and study protein-protein interactions.

**Correct Answer: C. Chromatography.**