**Core Concept**
The secondary immune response is characterized by the rapid production of antibodies, which is mediated by the activation of memory B cells. This response is crucial for providing immediate defense against pathogens that the immune system has encountered before.

**Why the Correct Answer is Right**
The correct answer is IgG. IgG antibodies are produced in high amounts and with great rapidity during the secondary response. This is because memory B cells, which are specific to the pathogen, are already present in the immune system and can quickly differentiate into plasma cells, which produce IgG antibodies. IgG antibodies are also highly effective at neutralizing pathogens and are the most abundant type of antibody in the serum.

**Why Each Wrong Option is Incorrect**
**Option A:** IgM is primarily produced during the primary response and is not as effective as IgG in neutralizing pathogens.
**Option B:** IgE is involved in allergic reactions and is not produced in high amounts during the secondary response.
**Option C:** IgA is primarily found in mucosal secretions and is not as effective as IgG in providing systemic immunity.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the secondary immune response is characterized by the rapid production of IgG antibodies, which provides immediate defense against pathogens. This is a key concept in understanding the body's immune response and is critical for the development of vaccines.

**Correct Answer: C. IgG.**