**Core Concept**
Ollier's disease is a rare genetic disorder characterized by the presence of multiple enchondromas, which are benign cartilaginous tumors within the bone. This condition affects the metaphyses of long bones, leading to abnormal growth and possible deformities.

**Why the Correct Answer is Right**
Ollier's disease involves the abnormal growth of cartilage within the bone, which leads to the formation of enchondromas. These tumors are thought to arise from the abnormal proliferation of chondrocytes, the cells responsible for cartilage production. The exact cause of Ollier's disease is still unknown, but it is believed to be related to mutations in the IDH1 or IDH2 genes, which play a critical role in the regulation of cellular metabolism.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the characteristic features of Ollier's disease.
**Option B:** This option is incorrect because it is a different genetic disorder that affects bone growth, but it does not involve enchondromas.
**Option C:** This option is incorrect because it is a type of bone tumor that is not associated with Ollier's disease.

**Clinical Pearl / High-Yield Fact**
Ollier's disease is often associated with a high risk of developing chondrosarcoma, a malignant tumor of cartilage, which highlights the importance of regular monitoring and follow-up for patients with this condition.

**Correct Answer:** C. Multiple enchondromas.