**Core Concept**
Paget's disease is a chronic bone disorder characterized by abnormal bone remodeling, leading to deformities and increased risk of fractures. It involves the replacement of normal bone tissue with disorganized and sclerotic bone, often causing bone pain, deformity, and potential complications such as osteosarcoma.

**Why the Correct Answer is Right**
The pelvis is the most commonly involved bone in Paget's disease due to its weight-bearing nature and high bone turnover rate. This increased bone turnover makes the pelvis more susceptible to the abnormal bone remodeling characteristic of Paget's disease. The pelvis's complex anatomy, with multiple bones and joints, also contributes to its frequent involvement.

**Why Each Wrong Option is Incorrect**
**Option A:** The skull is occasionally involved in Paget's disease, but it is not the most commonly affected bone. Skull involvement can lead to complications such as hearing loss and hydrocephalus.
**Option B:** The femur can be involved in Paget's disease, particularly in advanced cases, but it is not the most frequently affected bone. Femoral involvement can lead to significant deformity and increased risk of fracture.
**Option D:** Vertebrae can be involved in Paget's disease, but they are less commonly affected than the pelvis. Vertebral involvement can lead to kyphosis and other spinal deformities.

**Clinical Pearl / High-Yield Fact**
The "Paget's disease" mnemonic can help remember the classic triad of symptoms: pain (P), deformity (A), and fractures (G). This mnemonic can aid in the identification and management of patients with Paget's disease.

✓ Correct Answer: C. Pelvis