**Core Concept**
The isoelectric point (pI) of a protein is the pH at which the protein has no net charge, resulting from the balance between the positively charged amino groups and negatively charged carboxyl groups. This concept is crucial in understanding protein behavior, particularly in chromatography and electrophoresis.

**Why the Correct Answer is Right**
The isoelectric point can be determined by isoelectric focusing (IEF), a technique that separates proteins based on their charge. In IEF, a pH gradient is established in a gel matrix, and proteins migrate to their isoelectric point, where they remain stationary due to the balance of charges. This method is widely used in research and clinical settings for protein analysis and purification.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it does not specify a method for determining the isoelectric point of a protein. Isoelectric focusing is the correct technique for this purpose.

**Option B:** Chromatography is a broad technique used for separating and analyzing mixtures, but it is not specific to determining the isoelectric point of a protein.

**Option C:** Electrophoresis is a technique used to separate charged molecules based on their mobility, but it does not directly determine the isoelectric point of a protein.

**Clinical Pearl / High-Yield Fact**
Isoelectric focusing is a high-yield topic in biochemistry and clinical laboratory science. Remember that the isoelectric point is a unique characteristic of each protein, allowing it to be distinguished from others in a mixture.

**Correct Answer: C. Electrophoresis**