**Core Concept**
Myositis ossificans is a condition characterized by the abnormal formation of bone within muscle tissue, often as a result of trauma or injury. It involves the deposition of bone tissue in an area where it is not normally present, leading to a heterotopic ossification.

**Why the Correct Answer is Right**
In myositis ossificans, mature bone is formed through a process called endochondral ossification, where cartilage is first formed and then replaced by bone tissue. This process is mediated by the presence of osteoblasts, which are specialized cells responsible for bone formation. The mature bone seen in myositis ossificans is composed of a mixture of woven and lamellar bone, with a characteristic appearance on radiographs.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because myositis ossificans typically involves the formation of mature bone, not cartilage.
* **Option B:** This option is incorrect because fibrodysplasia ossificans progressiva is a different condition characterized by the progressive replacement of muscle and soft tissue with bone, but it is not the same as myositis ossificans.
* **Option C:** This option is incorrect because heterotopic ossification refers to the abnormal formation of bone in soft tissues, but it is a broader term that encompasses myositis ossificans as well as other conditions.

**Clinical Pearl / High-Yield Fact**
Myositis ossificans can be distinguished from other conditions that cause abnormal bone formation by its characteristic appearance on radiographs, which typically shows a mixture of woven and lamellar bone with a distinct cortical and medullary cavity.

**Correct Answer:** C.