**Core Concept**
The process of tooth mineralization is crucial for the development of strong and healthy teeth. This process involves the deposition of minerals such as calcium and phosphate into the tooth structure. **Enamel** and **dentin** are the two main components of the tooth that undergo mineralization.

**Why the Correct Answer is Right**
Mineralization of the teeth begins at the **cementum** and **enamel junction**, but more specifically, it starts with the formation of **dentin**, which is the layer beneath the enamel. The **odontoblasts** are the cells responsible for the formation of dentin. As the dentin forms, the **ameloblasts** begin to deposit enamel over the dentin, and this is where mineralization of the enamel starts.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because while the enamel is a critical component of the tooth, it is not where mineralization begins.
**Option B:** This option is also incorrect as the cementum, although important for tooth anchorage, is not the primary site for the initiation of tooth mineralization.
**Option D:** This option is incorrect because the initiation of mineralization is a highly regulated process that starts before the completion of the tooth structure.

**Clinical Pearl / High-Yield Fact**
Tooth mineralization is a complex process that involves the coordinated effort of multiple cell types, including **odontoblasts** and **ameloblasts**. Understanding this process is crucial for appreciating the development of dental structures and the prevention of dental diseases.

**Correct Answer:** Correct Answer: D. 3-4 months in utero.