**Core Concept**
The primary dentition, also known as baby teeth or deciduous teeth, consists of a specific number of teeth that begin to erupt when a child is about six months old. These teeth are crucial for the development of the oral cavity and surrounding structures. The normal development and number of primary teeth are essential for a child's overall health and dental well-being.

**Why the Correct Answer is Right**
The correct answer is based on the typical anatomy of the primary dentition in humans. Normally, children have a set of 20 primary teeth, which include incisors, canines, and molars. These teeth start erupting at around six months of age and continue to come in until the child is about three years old. The primary teeth play a vital role in the child's ability to chew, speak, and smile.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not match the standard number of primary teeth found in most children.
**Option B:** Similarly, this option does not correspond to the typical number of primary teeth.
**Option D:** This option is also incorrect as it does not align with the usual number of primary teeth.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the number of primary teeth can sometimes vary due to genetic conditions or developmental issues. However, the typical number of primary teeth is a fundamental aspect of pediatric dentistry and overall child health.

**Correct Answer: C. 20**