Immunity is provided by

Options

A. Erythrocytes
B. Lymphocytes
C. Megakaryocytes
D. Thrombocytes

Answer

### Step-by-Step Solution:

1. **Understanding Immunity**:
- Immunity is defined as the ability of an organism to resist infections or harmful foreign particles. It is the body's defense mechanism against pathogens.

2. **Identifying the Types of Blood Cells**:
- The question provides four options, each representing different types of blood cells: Erythrocytes (RBCs), Lymphocytes, Megakaryocytes, and Thrombocytes (Platelets).

3. **Analyzing Erythrocytes**:
- Erythrocytes, or red blood cells (RBCs), are primarily responsible for the transport of oxygen and carbon dioxide. They do not play a role in immunity. Therefore, Erythrocytes are not the answer.

4. **Examining Lymphocytes**:
- Lymphocytes are a type of white blood cell (WBC) that play a crucial role in the immune response. They can be further divided into B lymphocytes and T lymphocytes. B lymphocytes produce antibodies, while T lymphocytes help in the activation of B lymphocytes. This makes lymphocytes essential for providing immunity.

5. **Considering Megakaryocytes**:
- Megakaryocytes are large bone marrow cells responsible for the production of platelets, which are involved in blood clotting. They do not contribute to immunity, so they are not the answer.

6. **Reviewing Thrombocytes (Platelets)**:
- Thrombocytes, or platelets, are cell fragments derived from megakaryocytes and are primarily involved in the clotting process. They do not have a role in immunity, thus they are not the answer.

7. **Conclusion**:
- After evaluating all options, the only blood cell type that provides immunity is Lymphocytes. Therefore, the correct answer is **Lymphocytes**.