**Core Concept**
Hyperleukocytosis in Acute Myelogenous Leukemia (AML) refers to an elevated white blood cell count, often exceeding 100,000 cells/μL, which can lead to leukostasis, a potentially life-threatening complication. The goal of treatment is to rapidly reduce the white blood cell count and prevent leukostasis.

**Why the Correct Answer is Right**
Treatment for hyperleukocytosis in AML typically involves measures to rapidly reduce the white blood cell count, such as leukapheresis, high-dose corticosteroids, and chemotherapy. The primary aim is to prevent leukostasis by decreasing the viscosity of the blood and reducing the sheer force on blood vessels. This is crucial in children with AML who present with hyperleukocytosis.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not specified, but if it refers to allopurinol, it is incorrect because allopurinol is used to prevent tumor lysis syndrome, not to treat hyperleukocytosis.
**Option B:** This option is also not specified, but if it refers to hydroxyurea, it is incorrect because hydroxyurea can be used to manage leukocytosis in chronic myeloid leukemia but is not the preferred initial treatment for hyperleukocytosis in AML.
**Option C:** This option is not specified, but if it refers to supportive care, such as hydration and oxygen therapy, it is incorrect because while supportive care is essential, it is not a primary treatment for hyperleukocytosis.
**Option D:** This option is not specified, but if it refers to radiation therapy, it is incorrect because radiation therapy is not a standard treatment for hyperleukocytosis in AML.

**Clinical Pearl / High-Yield Fact**
It's essential to recognize that hyperleukocytosis in AML can lead to leukostasis, which is a medical emergency requiring rapid intervention. High-dose corticosteroids and leukapheresis are critical components of treatment in this scenario.

**Correct Answer: B. Hydroxyurea.**