When ever there is infection, the cells that are activated to phagocytes are  

Options

A. a. astrocytes
B. b. ependymal cells
C. c. microglial
D. d. oligodendrocytes

Answer

To answer the question "Whenever there is infection, the cells that are activated to phagocytes are," we need to analyze the options provided and understand the role of each cell type in the context of phagocytosis and immune response.

### Step-by-Step Solution:

1. **Identify the Cell Types**: The options provided are astrocytes, ependymal cells, microglial cells, and oligodendrocytes. All of these cells are associated with the central nervous system (CNS).

2. **Understand Phagocytosis**: Phagocytosis is the process by which certain cells, known as phagocytes, engulf and digest pathogens or debris. This process is crucial during infections to eliminate harmful agents.

3. **Evaluate Each Cell Type**:
- **Astrocytes**: These are star-shaped cells that provide structural support in the CNS. While they can perform phagocytosis, it is not their primary function.
- **Ependymal Cells**: These cells line the ventricles of the brain and are involved in the production of cerebrospinal fluid. They do not primarily function as phagocytes.
- **Microglial Cells**: These are the resident immune cells of the CNS. They are amoeboid in shape, highly motile, and possess numerous receptors that allow them to recognize and respond to pathogens effectively. They play a significant role in phagocytosis during infections.
- **Oligodendrocytes**: These cells are responsible for the formation of myelin in the CNS. They do not engage in phagocytosis.

4. **Determine the Most Relevant Cell Type**: Given the context of infection and the need for effective phagocytosis, microglial cells are the most relevant cell type. They are specifically activated during infections to clear pathogens and debris.

5. **Conclusion**: The cells that are activated to phagocytes during an infection are **microglial cells**.

### Final Answer:
**Microglial cells** are the cells activated to phagocytes during an infection.