**Core Concept:** Muscles in the human body are derived from the somites, which are formed during embryonic development from the presomitic mesoderm. In the case of the third arch, we are discussing the muscles that develop from the somites of the third pharyngeal arch.

**Why the Correct Answer is Right:** The correct answer, **D** (hyoglossus muscle), arises from the third pharyngeal arch, specifically from the myotome of the third somite. This muscle plays a crucial role in tongue movement and positioning.

**Why Each Wrong Option is Incorrect:**

**Option A (stylopharyngeus muscle)**: This muscle originates from the first and second pharyngeal arches, not the third.

**Option B (hyoid muscle)**: This muscle is part of the fourth pharyngeal arch and is not relevant to the third arch question.

**Option C (geniohyoid muscle)**: This muscle originates from the second and third pharyngeal arches but is not specifically from the third arch, making it an incorrect answer.

**Clinical Pearl / High-Yield Fact**: The third pharyngeal arch is significant in understanding embryonic development, as it contributes to various structures such as the hyoglossus, stylopharyngeus, and geniohyoid muscles. This knowledge is important for clinical reasoning and differential diagnosis in cases involving tongue movement or positioning issues.

**Correct Answer: Hyoglossus (D)**