Which of the following is not correctly matched ?

Options

A. Primary lymphoid organ : Thymus
B. Mucosa associated antibody : lgM Vaccination : Artificial active immunity
C. Vaccination : Artificial active immunity
D. Reservoirs of erythrocytes : Spleen

Answer

To solve the question "Which of the following is not correctly matched?", we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Identify the Options**:
We need to look at each option and determine if the pair is correctly matched or not. The options typically include pairs of terms related to lymphoid organs and their functions or characteristics.

2. **Evaluate the First Option**:
The first option mentions the **Thymus** as a primary lymphoid organ.
- **Analysis**: The thymus is indeed a primary lymphoid organ where T-cells mature.
- **Conclusion**: This option is correctly matched.

3. **Evaluate the Second Option**:
The second option states **Mucosa-associated antibody is matched with IgM** and **Artificial Active Immunity**.
- **Analysis**: Mucosa-associated antibodies are actually **IgA**, not IgM. Therefore, this option is incorrectly matched.
- **Conclusion**: This option is not correctly matched.

4. **Evaluate the Third Option**:
The third option mentions **Vaccination** matched with **Artificial Active Immunity**.
- **Analysis**: Vaccination does indeed lead to artificial active immunity as it involves introducing an antigen to stimulate an immune response.
- **Conclusion**: This option is correctly matched.

5. **Evaluate the Fourth Option**:
The fourth option states that the **Spleen** is a reservoir of **Erythrocytes** (red blood cells).
- **Analysis**: The spleen functions as a reservoir for red blood cells and filters blood.
- **Conclusion**: This option is correctly matched.

6. **Final Conclusion**:
After evaluating all options, the only incorrect match is the second option regarding mucosa-associated antibodies. Therefore, the answer to the question is that the second option is not correctly matched.

### Final Answer:
**The option that is not correctly matched is the second option: Mucosa-associated antibody is matched with IgM vaccination and Artificial Active Immunity.**