**Core Concept**
The reaction between antibody and soluble antigen is an example of an immune response, specifically an antigen-antibody reaction. This reaction is a critical aspect of immunology, enabling the body to recognize and neutralize pathogens, such as bacteria and viruses.

**Why the Correct Answer is Right**
The correct answer involves the Ouchterlony double diffusion technique, a laboratory method used to demonstrate the precipitation reaction between antibodies and soluble antigens. In this technique, antigen and antibody are placed in separate wells of an agar gel plate, allowing the immune complexes to form and precipitate, creating a visible precipitin line. The reaction is facilitated by the diffusion of both the antigen and antibody through the agar gel, enabling the formation of a visible precipitate.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe a method used to demonstrate the reaction between antibody and soluble antigen. While it may sound plausible, it is not a recognized laboratory technique.

**Option B:** This option is incorrect because it does not specifically describe the reaction between antibody and soluble antigen. It may be related to other immunological concepts, but it is not the correct answer.

**Option C:** This option is incorrect because it does not accurately describe the Ouchterlony double diffusion technique. While it may be a related concept, it is not the correct answer.

**Clinical Pearl / High-Yield Fact**
The Ouchterlony double diffusion technique is a useful tool for identifying and characterizing antigens and antibodies in the laboratory. It is often used in diagnostic immunology to identify the presence of specific antibodies or antigens in patient samples.

**Correct Answer: C. Ouchterlony double diffusion technique**