**Core Concept**
Cupping and fraying of metaphyses of long bones in children are characteristic radiographic findings in certain metabolic and genetic disorders. These changes result from altered bone growth and mineralization, leading to irregular metaphyseal ends.

**Why the Correct Answer is Right**
Lead poisoning, on the other hand, typically presents with dense metaphyseal bands or "lead lines" in long bones, rather than cupping and fraying. This is due to the toxic effects of lead on osteoblasts and the resulting abnormal bone matrix mineralization. The characteristic "lead lines" are a result of the dense, sclerotic bone formation in response to lead exposure.

**Why Each Wrong Option is Incorrect**
**Option A:** Rickets, a condition caused by vitamin D deficiency or phosphate/water imbalance, is characterized by cupping and fraying of metaphyses due to impaired mineralization of osteoid tissue.
**Option C:** Metaphyseal dysplasia, a group of disorders affecting metaphyseal growth, often presents with characteristic cupping and fraying of metaphyses.
**Option D:** Hypophosphatasia, a rare genetic disorder resulting from deficiency of tissue-nonspecific alkaline phosphatase, leads to defective bone mineralization and characteristic radiographic findings of cupping and fraying of metaphyses.

**Clinical Pearl / High-Yield Fact**
Remember that radiographic findings in pediatric bone disorders can be subtle and require a high index of suspicion. A thorough understanding of characteristic radiographic features is essential for accurate diagnosis and management.

**✓ Correct Answer: B. Lead poisoning**