**Core Concept**
The formation of dentin is a complex process involving the differentiation of odontoblasts, which are specialized cells responsible for producing the dentin matrix. Dentin is a key component of the tooth structure, making up the majority of the tooth's volume.

**Why the Correct Answer is Right**
The main bulk of dentin is formed by the process of intracellular dentinogenesis, where odontoblasts deposit collagen fibers and minerals into the dentin matrix. This process is mediated by the enzyme alkaline phosphatase, which catalyzes the formation of hydroxyapatite crystals. The dentin matrix is composed of about 70% inorganic materials, primarily hydroxyapatite, and 30% organic materials, including collagen and other proteins.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify the type of dentin or the cells involved in its formation.
**Option B:** This option is incorrect because it refers to the formation of enamel, which is a distinct process involving ameloblasts.
**Option C:** This option is incorrect because it refers to the formation of cementum, which is a thin layer of bone-like tissue covering the root of the tooth.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that dentin is a dynamic tissue that continues to form throughout life, a process known as secondary dentinogenesis. This process can be influenced by various factors, including age, diet, and oral health.

**Correct Answer:** C.