**Core Concept**
The question is testing the knowledge of dental development in children. At a certain age, children are expected to have a specific number of teeth, which is a normal part of their growth and development.

**Why the Correct Answer is Right**
Typically, a 9-year-old child should have a mix of primary and permanent teeth. By around 7-8 years of age, most children have lost their primary teeth and have started getting their permanent teeth. By 9 years, they should have around 20-28 permanent teeth, including incisors, canines, premolars, and molars. The exact number may vary depending on the child's individual growth and development.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not account for the mix of primary and permanent teeth that a 9-year-old child should have.
* **Option B:** This option is incorrect because it is too low for a 9-year-old child, who should have a significant number of permanent teeth by this age.
* **Option D:** This option is incorrect because it is too high for a 9-year-old child, who has not yet developed all of their permanent teeth.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that dental development can vary significantly among children, and some may develop their teeth earlier or later than others. However, a general guideline is that most children have lost their primary teeth and have started getting their permanent teeth by around 7-8 years of age.

**Correct Answer: C. 28.