**Core Concept**
Enamel formation is a critical stage in tooth development, and its completion marks a significant milestone. The process of enamel formation, also known as amelogenesis, is a complex interplay of cellular and molecular mechanisms that ultimately shape the tooth's structure.

**Why the Correct Answer is Right**
After enamel formation is complete, the tooth undergoes a period of maturation, during which the enamel becomes harder and more resistant to decay. This maturation process typically takes around three years, after which the tooth is ready to erupt through the gum tissue. The enamel's mineral content increases, and the crystalline structure becomes more organized, giving the tooth its characteristic hardness and durability. The eruption of the tooth is a gradual process, and it usually occurs when the tooth has reached a sufficient size and the surrounding bone and gum tissue have developed enough to accommodate it.

**Why Each Wrong Option is Incorrect**
**Option A:** One year is too short a time frame for the tooth to mature and become ready for eruption. The enamel formation process alone takes several years, and the maturation process adds to this duration.
**Option B:** Two years is closer but still underestimates the time required for the tooth to mature and erupt. The process involves complex cellular and molecular mechanisms that cannot be rushed.
**Option D:** Four years is excessive, as the tooth will typically erupt within three years after enamel formation is complete.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that enamel formation is a prolonged process that continues until the tooth erupts. The maturation period allows the enamel to reach its maximum hardness and durability, making it more resistant to decay and wear.

✓ Correct Answer: C. Three years