**Core Concept:** Synchondroses are cartilaginous joints that undergo endochondral ossification to form bone. The process involves the differentiation of chondrocytes into osteoblasts, which then deposit bone matrix. There are three types of synchondroses:

1. **Endochondral:** This type of synchondrosis completes first, followed by the other types.
2. Intervertebral disk: This is an example of a fibrocartilaginous joint that does not undergo endochondral ossification.
3. Syndesmoses and sutures: These are fibrous and synlacinous joints, respectively, and do not undergo endochondral ossification.

**Why the Correct Answer is Right:** The correct answer, option C (Endochondral), refers to the type of synchondrosis that completes first. In endochondral ossification, the cartilage is replaced by bone tissue. This process starts from the periphery of the cartilage towards the center, which allows the cartilage to be gradually replaced by bone.

**Why Each Wrong Option is Incorrect:**

A. **Intervertebral disk:** This is a fibrocartilaginous joint that does not undergo endochondral ossification. Instead, it undergoes proteoglycan synthesis and cross-linking, which provides its unique viscoelastic properties.

B. **Syndesmoses and sutures:** These are fibrous and synlacinous joints, respectively, that do not undergo endochondral ossification. The process of ossification is not applicable to these types of joints.

C. **Fibrocartilage:** Fibrocartilage is a type of cartilage found in joints like the intervertebral disk, not synchondroses. Fibrocartilage differs from hyaline cartilage, which is found in synchondroses, as it has a more dense collagen matrix and lacks a layer of chondrocytes.

**Clinical Pearl:** Understanding the different types of joints and their features is essential for understanding the pathophysiology of joint diseases, such as osteoarthritis. For example, in osteoarthritis, the articular cartilage undergoes damage and degeneration, affecting joint mobility and leading to pain and stiffness.