**Core Concept**
The angle of the mandible refers to the curvature of the lower jawbone. In dentistry and anatomy, the angle of the mandible is classified based on its shape and orientation. An obtuse angle of the mandible indicates a specific type of curvature.

**Why the Correct Answer is Right**
An obtuse angle of the mandible is characteristic of a prognathic mandible. This means that the lower jawbone protrudes forward, resulting in an increased overjet and an obtuse angle between the mandible and the maxilla. The prognathic mandible is often associated with a Class III malocclusion, where the lower teeth overlap the upper teeth.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because an obtuse angle of the mandible is not characteristic of a retrognathic mandible, which is typically associated with a Class II malocclusion and a reduced overjet.
* **Option B:** This option is incorrect because an obtuse angle of the mandible is not typical of a normal or orthognathic mandible, which has a more neutral or slightly concave curvature.
* **Option C:** This option is incorrect because an obtuse angle of the mandible is not characteristic of a mandible with a horizontal or straight curvature, which is often associated with a Class I malocclusion.

**Clinical Pearl / High-Yield Fact**
In orthodontics, the angle of the mandible is an important factor in determining the treatment plan for malocclusions. A prognathic mandible often requires a more aggressive treatment approach to correct the overjet and improve the aesthetics and function of the bite.

**Correct Answer:** C.