**Core Concept:** Osteoclastoma is a benign tumor of bone, characterized by excessive bone resorption by osteoclasts, which are multinucleated cells responsible for maintaining bone remodeling.

**Why the Correct Answer is Right:** Osteoclastomas predominantly affect individuals during their second to fourth decade of life. The increased prevalence in this age group is due to the rapid bone growth and remodeling that occurs during adolescence and young adulthood.

**Why Each Wrong Option is Incorrect:**

A. Children: While osteoclastomas can occur in children, they are less common in this age group, accounting for approximately 10% of cases.

B. Elderly: Osteoclastomas typically affect younger individuals, making it less common in the elderly population.

C. Middle-aged adults: Similar to option A, osteoclastomas are more common in the second to fourth decade of life, making this option incorrect as well.

**Clinical Pearl:** The age distribution of osteoclastomas is a crucial piece of information for clinicians, as it helps guide diagnosis and treatment decisions.

**Correct Answer:** **D. Second to Fourth Decade:** Osteoclastomas are more common in individuals between the ages of 20 to 40, reflecting the active bone remodeling and growth in this age group.