Which of the following is the least and most abundant leucocytes in human blood, respectively ?

Options

A. Basophils , Neutrophils
B. Neutrophils , Basophils
C. Eosinophil's , Neutrophils
D. Basophils, Lymphocytes

Answer

To determine the least and most abundant leukocytes in human blood, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Types of Leukocytes**:
- Leukocytes, or white blood cells, are classified into different types: neutrophils, lymphocytes, monocytes, eosinophils, and basophils.

2. **Identify the Most Abundant Leukocyte**:
- Among these types, neutrophils are known to be the most abundant leukocytes in human blood. They typically make up about 50-70% of the total white blood cell count. Their primary function is to combat bacterial and fungal infections.

3. **Identify the Least Abundant Leukocyte**:
- Basophils are recognized as the least abundant leukocytes, constituting about 0.5-1% of the total white blood cell count. They play a role in allergic responses and inflammation.

4. **Evaluate the Options**:
- Given the options:
1. Basophils and Neutrophils
2. Neutrophils and Basophils
3. Eosinophils and Neutrophils
4. Basophils and Lymphocytes
- The first option states Basophils (least abundant) and Neutrophils (most abundant), which is correct.

5. **Conclusion**:
- The correct answer is **Basophils (least abundant) and Neutrophils (most abundant)**.

### Final Answer:
The least and most abundant leukocytes in human blood are **Basophils** and **Neutrophils**, respectively.

---