Assertion : Monocytes constitute only 6-8% of WBCs but are very essential
Reason: These are phagocytic cells.

Options

A. Both A and R are true and R is the correct explanation of A.
B. Both A and R are true but R is not correct explanation of A
C. A is true but R is false
D. A and R are false

Answer

**Step-by-Step Solution:**

1. **Understanding the Assertion:**
- The assertion states that monocytes constitute only 6-8% of white blood cells (WBCs) but are very essential.
- Monocytes are a type of agranulocyte, which is a category of WBCs.

2. **Evaluating the Percentage:**
- It is a fact that monocytes make up about 6-8% of the total WBC count in a healthy individual. This percentage is accurate and confirms the assertion.

3. **Understanding the Reason:**
- The reason provided states that monocytes are phagocytic cells.
- Phagocytic cells are those that can engulf and digest foreign particles, such as bacteria and dead cells.

4. **Linking the Assertion and Reason:**
- Monocytes, being phagocytic, play a crucial role in the immune system by removing pathogens and dead cells from the body.
- Their ability to fight against infections and cancer cells highlights their essential role in maintaining health.

5. **Conclusion:**
- Both the assertion and the reason are true.
- The reason correctly explains why monocytes, despite their small percentage, are essential for the body.

6. **Final Answer:**
- Therefore, the correct answer is option A: Both assertion and reason are true, and the reason is the correct explanation of the assertion.

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