## Core Concept
Neutropenia is a condition characterized by an abnormally low number of neutrophils, which are a type of white blood cell crucial for fighting infections. The severity of neutropenia is typically classified based on the absolute neutrophil count (ANC). Understanding the classification helps in determining the risk of infection and guiding management.

## Why the Correct Answer is Right
The correct answer for moderate neutropenia is an ANC of 500-999 cells/μL. This classification is important because it helps predict the risk of infection. Patients with moderate neutropenia have a higher risk of developing infections compared to those with mild neutropenia but a lower risk compared to those with severe neutropenia. The ANC is a critical measure used to assess the severity of neutropenia.

## Why Each Wrong Option is Incorrect
- **Option A:** 1500 cells/μL is generally considered within the normal range or mild neutropenia, depending on the reference range used, and is not indicative of moderate neutropenia.

## Clinical Pearl / High-Yield Fact
A key point to remember is that the risk of infection increases as the ANC decreases. Patients with moderate neutropenia (ANC 500-999 cells/μL) may require closer monitoring and possibly antimicrobial prophylaxis, depending on the underlying cause and clinical context.

## Correct Answer: B. 500-999 cells/μL.