## Core Concept
The question pertains to the developmental timeline of deciduous (primary) teeth pulp, encompassing both prenatal and postnatal development phases, as well as the period of regression. Deciduous teeth begin developing during fetal development and continue to develop and function until they are shed and replaced by permanent teeth.

## Why the Correct Answer is Right
The development of deciduous teeth starts prenatally, with the first primary teeth (incisors) beginning to calcify around 3-4 months in utero. The process of development and eruption continues postnatally, with the first deciduous tooth erupting around 6 months of age, and the last one around 3 years of age. The lifespan of the deciduous pulp, therefore, spans from early fetal development to the time these teeth are shed, which typically occurs between 6 to 12 years of age. Given this timeline, the maximum life of the deciduous pulp, including both prenatal and postnatal development and the period of regression, approximates 12-13 years.

## Why Each Wrong Option is Incorrect
- **Option A:** This option suggests a significantly shorter lifespan than what is known for deciduous teeth development and function.
- **Option B:** Similarly, this option underestimates the total lifespan of deciduous pulp development and function.
- **Option D:** This option overestimates the lifespan, as deciduous teeth typically start being shed and replaced by permanent teeth well before this age.

## Clinical Pearl / High-Yield Fact
A key point to remember is that the deciduous teeth begin to develop in utero and continue to erupt and function until they are lost. Understanding the timeline of dental development is crucial for pediatric dentistry and orthodontics. A helpful mnemonic or fact is that the first deciduous teeth start calcifying at 3 months in utero and the first tooth erupts at 6 months of age.

**Correct Answer: C. 12-13 years.**