**Core Concept**
The eruption of a tooth is a complex process involving the coordinated effort of multiple factors, including the resorption of surrounding bone, the expansion of the periodontal ligament, and the upward movement of the tooth germ. This process is crucial for the proper alignment and positioning of teeth in the oral cavity.

**Why the Correct Answer is Right**
The correct answer is related to the process of cementum resorption, which is a key factor in tooth eruption. Cementum is a thin layer of bone-like tissue covering the root of a tooth. The resorption of cementum by osteoclasts creates a small space between the tooth and the surrounding bone, allowing the tooth to move upward and erupt into the oral cavity. This process is mediated by specific enzymes and receptors, including cathepsin K and RANKL.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not directly relate to the process of tooth eruption. While the periodontal ligament plays a crucial role in tooth support and movement, its expansion is not the primary factor in tooth eruption.

**Option B:** This option is incorrect because it is a process that occurs in bone remodeling, not tooth eruption. Bone resorption is an essential process in bone health, but it is not directly involved in tooth eruption.

**Option C:** This option is incorrect because it is a type of cell that is involved in bone remodeling, not tooth eruption. Osteoclasts are responsible for bone resorption, but they are not the primary cells involved in tooth eruption.

**Clinical Pearl / High-Yield Fact**
A key factor in tooth eruption is the balance between osteoclastic resorption and osteoblastic deposition. An imbalance in this process can lead to various dental and skeletal disorders, including tooth impaction and malocclusion.

**Correct Answer: C. Osteoclasts**