**Core Concept**
Immunoglobulins (Ig) play a crucial role in the immune system by recognizing and binding to specific pathogens, leading to their neutralization or elimination. Opsonization is the process by which a pathogen is marked for destruction by the immune system, typically through the binding of an antibody to the pathogen's surface.

**Why the Correct Answer is Right**
IgG is the primary immunoglobulin responsible for opsonization. This is due to its ability to bind to the Fc receptor on phagocytic cells, such as macrophages and neutrophils, which then engulf and digest the opsonized pathogen. IgG's ability to cross the placenta and provide long-term immunity also makes it an essential component of the immune system.

**Why Each Wrong Option is Incorrect**
* **Option A:** IgM is primarily involved in the early immune response and is not typically associated with opsonization.
* **Option B:** IgA is primarily involved in mucosal immunity and is not typically associated with opsonization.
* **Option C:** IgE is primarily involved in allergic reactions and is not typically associated with opsonization.

**Clinical Pearl / High-Yield Fact**
IgG is the only immunoglobulin that can cross the placenta, providing essential passive immunity to the fetus. This unique property makes IgG a critical component of prenatal immunization strategies.

**Correct Answer:** C. IgG is the primary immunoglobulin responsible for opsonization.