Which of the following is correctly paired?

Options

A. Basophils - Are not involved in inflammatory or allergic reactions
B. Eosinophils - Stained by methylene blue
C. Monocytes - Largest leucocytes
D. Neutrophils - Kidney shaped nucleus

Answer

To solve the question of which of the following is correctly paired, we will analyze each option provided in the context of the characteristics of the respective blood cells.

### Step-by-Step Solution:

1. **Identify the Options**: We need to evaluate the four options provided in the question regarding blood cells and their characteristics.

2. **Evaluate Option 1**:
- **Statement**: Basophils are not involved in any inflammatory or allergic reactions.
- **Analysis**: This statement is incorrect. Basophils are indeed involved in allergic reactions and inflammation, particularly in IgE-dependent responses.
- **Conclusion**: This option is not correctly paired.

3. **Evaluate Option 2**:
- **Statement**: Eosinophils stained by methylene blue.
- **Analysis**: Eosinophils are typically stained using eosin or Wright's stain, not methylene blue. Methylene blue is used for staining other types of cells.
- **Conclusion**: This option is not correctly paired.

4. **Evaluate Option 3**:
- **Statement**: Monocyte is the largest leukocyte.
- **Analysis**: This statement is correct. Monocytes are indeed the largest type of white blood cell (leukocyte) and can differentiate into macrophages and dendritic cells.
- **Conclusion**: This option is correctly paired.

5. **Evaluate Option 4**:
- **Statement**: Neutrophils have a kidney-shaped nucleus.
- **Analysis**: This statement is incorrect. Neutrophils have a multi-lobed nucleus, while monocytes have a kidney-shaped nucleus.
- **Conclusion**: This option is not correctly paired.

### Final Answer:
Based on the evaluations, the only correctly paired statement is:
**Option 3: Monocyte is the largest leukocyte.**