**Core Concept**
The skeletal classification of malocclusion refers to the assessment of the relationship between the maxilla and mandible, which is crucial in orthodontic diagnosis and treatment planning. This classification helps in identifying the underlying skeletal issues that may be contributing to the malocclusion.

**Why the Correct Answer is Right**
The correct answer is based on the Angle's classification, which is a widely accepted method for classifying malocclusion based on the skeletal relationship between the maxilla and mandible. According to Angle's classification, Class I malocclusion is characterized by normal or near-normal skeletal relationships, Class II malocclusion is characterized by a retrognathic maxilla or prognathic mandible, and Class III malocclusion is characterized by a prognathic maxilla or retrognathic mandible. This classification helps in understanding the underlying skeletal issues and planning appropriate treatment.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify a recognized classification system for skeletal malocclusion. There are various classification systems, but the question is likely referring to the most widely accepted one.
**Option B:** This option is incorrect because it is not a recognized classification system for skeletal malocclusion. The correct classification systems focus on the relationship between the maxilla and mandible, not the shape or size of the teeth.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that a thorough orthodontic diagnosis involves not only a detailed examination of the teeth and their relationships but also a careful assessment of the underlying skeletal relationships. This helps in identifying the root cause of the malocclusion and planning an effective treatment plan.

**Correct Answer: D. Angle's classification**