**Core Concept**
Fibrous dysplasia is a benign fibro-osseous disorder characterized by the abnormal growth of fibrous tissue within the bone, leading to a replacement of normal bone with a mixture of fibrous tissue and immature bone. This results in a disturbance in the normal bone architecture, which can be visualized on radiographs.

**Why the Correct Answer is Right**
The characteristic radiological feature of fibrous dysplasia is the ground glass appearance, which is due to the uniform, homogenous replacement of normal bone with fibro-osseous tissue. This appearance is typically seen on radiographs, where the affected bone appears to have a ground glass or soap bubble appearance due to the presence of multiple small, well-defined radiolucent areas within the bone. The ground glass appearance is a result of the mixture of fibrous tissue and immature bone, which lacks the normal trabecular pattern and cortical bone structure.

**Why Each Wrong Option is Incorrect**
**Option A:** Thickened bone matrix is not a characteristic feature of fibrous dysplasia. Instead, the bone matrix in fibrous dysplasia is often thinned and expanded due to the replacement of normal bone with fibro-osseous tissue.
**Option B:** Cortical erosion is not a typical feature of fibrous dysplasia. While fibrous dysplasia can lead to thinning of the cortical bone, cortical erosion is more commonly associated with other bone disorders such as osteomyelitis or bone tumors.
**Option D:** Bone enlargement is a non-specific feature that can be seen in a variety of bone disorders, including fibrous dysplasia. However, bone enlargement is not a characteristic feature of fibrous dysplasia, and other features such as the ground glass appearance are more specific.

**Clinical Pearl / High-Yield Fact**
Fibrous dysplasia can be distinguished from other bone disorders such as osteosarcoma or osteoblastoma, which often present with a more aggressive radiological appearance and cortical destruction.

✓ Correct Answer: C. Ground glass appearance