## **Core Concept**
The question tests understanding of the immune response, specifically the types of antibodies produced in response to an antigen. Ovalbumin, a protein found in egg whites, acts as an antigen when injected into a rabbit, triggering an immune response. The primary immune response involves the production of specific classes of antibodies.

## **Why the Correct Answer is Right**
The initial immune response to an antigen like ovalbumin primarily involves the production of **IgM antibodies**. IgM is the first class of antibodies produced in response to an infection or antigen exposure. It is a pentameric antibody that provides immediate protection. The production of IgM is followed by a class switch to other antibody types, such as IgG, IgA, or IgE, but initially, IgM is the predominant antibody.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because it does not specify IgM as the initial antibody response.
- **Option B:** This option might suggest another class of antibodies but is incorrect because it does not accurately represent the initial immune response.
- **Option D:** This option is incorrect because it likely represents a later or different type of immune response.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that **IgM is the first antibody produced in response to an antigen** and is indicative of a primary immune response. This is crucial for understanding immunological diagnostics and the timeline of infections.

## **Correct Answer:** .