**Core Concept**
In newborn children, the mandible (lower jawbone) is relatively small compared to the maxilla (upper jawbone), resulting in a characteristic facial appearance. This anatomical feature is due to the differential growth rates of the two bones during fetal development.

**Why the Correct Answer is Right**
The correct answer, mandibular retrusion, is a normal finding in newborns. This occurs because the maxilla grows more rapidly than the mandible during fetal development, causing the lower jaw to be relatively underdeveloped. The maxilla and mandible are formed from separate embryonic structures, which grow and develop at different rates, resulting in this characteristic facial appearance. This phenomenon is a normal variant in newborns and is not indicative of any underlying pathology.

**Why Each Wrong Option is Incorrect**
**Option A:** Maxillary protrusion is not typically seen in newborns, as the maxilla is generally larger than the mandible.
**Option B:** Maxillary retrusion is not a characteristic finding in newborns, as the maxilla is typically well-developed compared to the mandible.
**Option C:** Mandibular protrusion is not a normal finding in newborns, as the mandible is relatively underdeveloped compared to the maxilla.

**Clinical Pearl / High-Yield Fact**
In newborns, the mandibular retrusion is a normal variant that should not be mistaken for any underlying pathology. It is essential to consider the differential growth rates of the maxilla and mandible when evaluating the facial appearance of newborns.

**✓ Correct Answer: D. Mandibular retrusion**