In a healthy adult man, the smallest type of leucocytes are

Options

A. Basophils
B. monocytes
C. eosinophils
D. lymphocytes

Explanation

To determine the smallest type of leucocytes in a healthy adult man, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Types of Leucocytes**: Leucocytes, or white blood cells, are classified into different types based on their size and function. The main types include:
- Neutrophils
- Lymphocytes
- Monocytes
- Eosinophils
- Basophils

2. **Compare Sizes of Leucocytes**:
- Monocytes are the largest type of leucocyte.
- Eosinophils are smaller than monocytes but larger than lymphocytes.
- Basophils are also larger than lymphocytes.
- Lymphocytes are known to be the smallest type of leucocyte.

3. **Identify the Smallest Leucocyte**: Based on the size comparison, lymphocytes are the smallest type of leucocyte in a healthy adult man.

4. **Select the Correct Answer**: From the options given:
- A. Basophil
- B. Monocyte
- C. Eosinophil
- D. Lymphocyte

The correct answer is **D. Lymphocyte**.

### Final Answer:
The smallest type of leucocytes in a healthy adult man is **Lymphocyte**.

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