To find the correct descending order of percentage proportion of leucocytes (white blood cells) in human blood, we need to know the typical percentage of each type of leucocyte. Here’s the breakdown:
1. **Neutrophils**: These are the most abundant type of white blood cells, constituting about 60-65% of the total leukocyte count.
2. **Lymphocytes**: These cells make up approximately 20-25% of the total leukocyte count.
3. **Monocytes**: They account for about 6-8% of the total leukocyte count.
4. **Eosinophils**: These cells typically represent about 2-3% of the total leukocyte count.
5. **Basophils**: These are the least abundant, constituting about 0.5-1% of the total leukocyte count.
Now, let's arrange them in descending order based on their percentages:
1. **Neutrophils**: 60-65%
2. **Lymphocytes**: 20-25%
3. **Monocytes**: 6-8%
4. **Eosinophils**: 2-3%
5. **Basophils**: 0.5-1%
Thus, the correct descending order of leucocytes in human blood is:
**Neutrophils > Lymphocytes > Monocytes > Eosinophils > Basophils**
Now, let's match this order with the options provided:
- a. Neutrophils, Lymphocytes, Monocytes, Eosinophils, Basophils (Correct)
- b. Neutrophils, Basophils, Lymphocytes, Eosinophils, Monocytes (Incorrect)
- c. Neutrophils, Monocytes, Lymphocytes, Eosinophils, Basophils (Incorrect)
- d. Neutrophils, Eosinophils, Basophils, Lymphocytes, Monocytes (Incorrect)
The correct answer is **option A**: Neutrophils, Lymphocytes, Monocytes, Eosinophils, and Basophils.
