The antibody involved in secondary immune responses which activates of basophils is

Options

A. IgA
B. IgM
C. IgG
D. IgD

Answer

To determine the antibody involved in secondary immune responses that activates basophils, we can analyze the options provided: IgA, IgM, IgG, and IgD.

### Step-by-Step Solution:

1. **Understanding the Immune Response**:
- The immune system has two main types of responses: primary and secondary. The primary response occurs when the body encounters an antigen for the first time, while the secondary response occurs upon subsequent exposures to the same antigen.

2. **Identifying the Antibodies**:
- **IgD**: This antibody is primarily involved in signaling B cells for activation. It does not play a significant role in secondary immune responses. Therefore, IgD is not the correct answer.

- **IgA**: This antibody is found in mucosal areas and bodily secretions such as colostrum, tears, and sweat. It is more associated with the primary immune response rather than the secondary response. Thus, IgA is also not the correct answer.

- **IgM**: This is the first antibody produced in response to an infection and is primarily associated with the primary immune response. It does not play a significant role in activating basophils during secondary responses. Hence, IgM is not the correct answer.

- **IgG**: This antibody is the most abundant in the blood and is specifically involved in the secondary immune response. It is responsible for recognizing and responding to pathogens that the body has encountered before. IgG also activates basophils, making it the correct answer.

3. **Conclusion**:
- Based on the analysis, the antibody involved in secondary immune responses that activates basophils is **IgG**.

### Final Answer:
**IgG**