[A] : Macrophage is a large amoeboid cell that can engulf, ingest and destroy bacteria, damaged cells and worn-out red blood cells. This process is called phagocytosis and is an important part of the body s defence against disease.
[R]: Macrophages are found free (wandering) in the tissues, in connective tissue (as histiocytes), in the lining of the blood sinusoids of the liver (as Kupffer cells), and in lymphoid tissue. They make up the reticulo-endothelial system.

Options

A. (a) If both A and R are true and R is the correct explanation of A
B. (b) If both A and R are true but R is not the correct explanation of A
C. (c) If A is true and R is false
D. (d) If both A and R are false

Answer

To solve the assertion-reason question regarding macrophages, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Assertion**:
- The assertion states that macrophages are large amoeboid cells capable of engulfing, ingesting, and destroying bacteria, damaged cells, and worn-out red blood cells through a process called phagocytosis. This is indeed true as macrophages play a vital role in the immune response.

2. **Understand the Reason**:
- The reason explains that macrophages are found in various forms throughout the body, including as histiocytes in connective tissue, Kupffer cells in the liver, and as part of the reticuloendothelial system. This statement is also true, as macrophages exist in different forms depending on their location in the body.

3. **Evaluate the Relationship**:
- We need to determine if the reason provided correctly explains the assertion. Since the assertion highlights the role of macrophages in the immune defense, and the reason describes their various forms and locations, it can be concluded that the reason supports the assertion by explaining how macrophages function in different tissues.

4. **Conclude**:
- Since both the assertion and the reason are true, and the reason provides a correct explanation for the assertion, we can conclude that the answer is option A: both assertion and reason are true, and the reason is the correct explanation of the assertion.

### Final Answer:
- **Both assertion and reason are true, and the reason is the correct explanation of the assertion.**

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