**Core Concept**
The Sella-Nasion-A point (SNA) is a cephalometric measurement used to assess the position of the maxilla in relation to the cranial base. An increased SNA angle indicates a protrusive maxilla.

**Why the Correct Answer is Right**
An SNA angle of 90° is considered abnormal and suggests a Class II skeletal pattern. This is because the maxilla is positioned more anteriorly than usual, which can be associated with a narrow upper airway, increased risk of sleep apnea, and other orthodontic issues. The normal SNA range is typically between 75° and 85°.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not provided.
**Option B:** This option is not provided.
**Option C:** This option is not provided.
**Option D:** This option is not provided.

**Clinical Pearl / High-Yield Fact**
A protrusive maxilla (increased SNA angle) can be associated with a narrow upper airway, making it a potential risk factor for sleep apnea. Dentists and orthodontists should consider this when evaluating patients with a Class II skeletal pattern.

**Correct Answer:** C. Class II skeletal pattern.