**Core Concept**
The process of ossification is a complex process where cartilaginous models are replaced by bone tissue. The first bone to undergo this process is a crucial aspect of skeletal development, marking the beginning of the transition from a cartilaginous skeleton to a bony one.

**Why the Correct Answer is Right**
The first bone to ossify is the clavicle, which begins to ossify around the 6th to 8th week of gestation. This process is mediated by the action of osteoblasts, which are cells responsible for bone matrix deposition. The clavicle's early ossification is thought to be due to its unique embryological origin, which involves the fusion of multiple cartilaginous elements.

**Why Each Wrong Option is Incorrect**
**Option A:** The sternum, while undergoing ossification, does not do so as early as the clavicle. Its ossification centers appear later in development.
**Option B:** The ribs also undergo ossification, but their process begins slightly later than that of the clavicle.
**Option C:** The long bones of the limbs, such as the femur and humerus, ossify later in development, typically after the clavicle.

**Clinical Pearl / High-Yield Fact**
The clavicle's early ossification is a key landmark in fetal development, allowing for the assessment of gestational age and fetal maturity on radiographs.

**Correct Answer:** C. Clavicle.