## **Core Concept**
The normal leucocyte count, also known as the white blood cell (WBC) count, is a crucial parameter in assessing the body's immune response. Leucocytes or white blood cells are an essential part of the immune system, helping to fight infections and diseases. The normal range for the leucocyte count in adults is generally considered to be between 4,000 and 11,000 cells per microliter (µL) of blood.

## **Why the Correct Answer is Right**
The correct answer, , falls within the widely accepted normal range for leucocyte count. This range can slightly vary between laboratories due to differences in measurement techniques and reference populations. However, a count of is well within the normal limits, indicating a healthy immune response capability.

## **Why Each Wrong Option is Incorrect**
- **Option A:** is considered leukopenic, which means there are not enough white blood cells. This can increase the risk of infections.
- **Option B:** is slightly below the normal range, also indicating leukopenia.
- **Option D:** is above the normal range, indicating leukocytosis, which can be a response to infection, inflammation, or other medical conditions.

## **Clinical Pearl / High-Yield Fact**
A normal leucocyte count is crucial for the body's defense against pathogens. An abnormal count, either too high or too low, can indicate an underlying health issue that needs medical attention. For example, a very low WBC count (leukopenia) can make a person more susceptible to infections, while a very high WBC count (leukocytosis) can be a sign of infection, inflammation, or leukemia.

## **Correct Answer:** .