**Core Concept**
The question is testing the understanding of the process of immunophenotyping, which is used to identify and classify cells based on their specific antigen receptors. This process is crucial in the diagnosis and management of various hematological disorders.

**Why the Correct Answer is Right**
The process of separating cells based on specific antigen receptors is achieved through a technique called Fluorescence-Activated Cell Sorting (FACS). FACS utilizes fluorescently labeled antibodies that bind to specific antigens on the surface of cells, allowing for the identification and separation of cells with specific antigen receptors. The labeled cells are then sorted based on their fluorescence intensity, enabling the isolation of cells with specific surface markers.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify a technique for separating cells based on antigen receptors. While flow cytometry is related to FACS, it is not the correct answer.

**Option B:** This option is incorrect because it refers to a technique used for analyzing the structure of cells, not for separating them based on antigen receptors.

**Option C:** This option is incorrect because it refers to a type of microscopy used to visualize cells, not for separating them based on antigen receptors.

**Clinical Pearl / High-Yield Fact**
FACS is a high-yield technique used in immunophenotyping, and it is essential to understand its principles and applications in diagnosing hematological disorders.

**Correct Answer:** C. Flow Cytometry