**Core Concept**
Malignant bone tumors are rare, aggressive, and destructive lesions that arise from the bone tissue. They can be primary (originating from bone cells) or secondary (metastasizing from other cancers).

**Why the Correct Answer is Right**
The most common primary malignant bone tumor is Osteosarcoma, also known as osteogenic sarcoma. It arises from the osteoblasts, which are the bone-forming cells. Osteosarcoma typically affects the metaphysis of long bones, particularly the femur (thigh bone) and tibia (shin bone). It is characterized by the uncontrolled proliferation of malignant cells that produce abnormal bone matrix, leading to the formation of osteoid tissue.

**Why Each Wrong Option is Incorrect**
**Option A:** Chondrosarcoma is a type of malignant cartilage tumor, but it is less common than osteosarcoma.
**Option B:** Ewing's sarcoma is a highly malignant tumor that arises from the bone marrow, but it is more common in children and adolescents.
**Option C:** Multiple myeloma is a type of plasma cell malignancy that affects the bone marrow, but it is not a primary bone tumor.

**Clinical Pearl / High-Yield Fact**
Osteosarcoma is often associated with a poor prognosis, especially if it is diagnosed at an advanced stage. However, with the advent of chemotherapy and limb-salvage surgery, the 5-year survival rate has improved significantly.

**Correct Answer: D. Osteosarcoma**