At the age of 9 years, the number of permanent teeth is –

**Core Concept**
The question is testing the student's knowledge of dental development and eruption. Human dentition is divided into two categories: primary teeth (also known as baby teeth) and permanent teeth. The primary teeth start erupting when a child is around 6 months old and continue to erupt until they are about 3 years old. After the primary teeth start to fall out, the permanent teeth begin to erupt and continue to do so until the age of 14 in girls and 16 in boys.

**Why the Correct Answer is Right**
At the age of 9 years, most children have a mix of primary and permanent teeth in their mouth. However, by this age, the first permanent teeth, also known as the first molars and incisors, have usually started to erupt. The first permanent teeth to erupt are typically the first molars, which start to come in between the ages of 6 to 7 years. The incisors follow, with the upper central incisors usually coming in between the ages of 7 to 8 years and the lower central incisors between the ages of 8 to 9 years.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify the number of permanent teeth.
**Option B:** This option is incorrect because it is not a specific number, and it is also not a correct range for the number of permanent teeth at the age of 9 years.
**Option C:** This option is incorrect because it is a number that is too high for the age of 9 years, considering most children have not yet had all of their primary teeth replaced with permanent teeth.

**Clinical Pearl / High-Yield Fact**
It's essential for pediatric dentists and general practitioners to keep track of the eruption times of primary and permanent teeth in children to provide proper dental care and address any potential issues early on.

**Correct Answer: C. 12.