**Core Concept**
Tooth formation, or **odontogenesis**, involves several stages, including initiation, morphodifferentiation, and apposition. The stage characterized by the commencement of **mineralization** and **root formation** is a critical period in tooth development.

**Why the Correct Answer is Right**
The correct stage is characterized by the deposition of minerals, leading to the hardening of dental tissues, and the initiation of **root formation**, which is essential for tooth anchorage. This stage is marked by the activity of **odontoblasts**, which produce **dentin**, and the formation of **cementum** by **cementoblasts**.

**Why Each Wrong Option is Incorrect**
**Option A:** Is incorrect because it refers to an earlier stage of tooth development.
**Option B:** Is also incorrect as it is associated with a different aspect of tooth formation.
**Option D:** Does not correspond with the commencement of mineralization and root formation.

**Clinical Pearl / High-Yield Fact**
The stage of tooth formation characterized by mineralization and root formation is crucial for the development of a healthy, functional tooth. Any disruption during this stage can lead to dental anomalies.

**Correct Answer:** C. Apposition