**Core Concept**
The lateral movement of the jaw, also known as lateral excursion, involves the coordinated action of several muscles to move the mandible from side to side. This movement is essential for functions such as chewing and speaking.

**Why the Correct Answer is Right**
The correct answer involves the muscles responsible for the lateral movement of the jaw. The lateral pterygoid muscle is a key player in this movement, as it helps to move the condyle of the mandible in a lateral direction. This is achieved through the action of the superior and inferior heads of the lateral pterygoid muscle. The medial pterygoid muscle also assists in this movement by helping to rotate the mandible.

**Why Each Wrong Option is Incorrect**
**Option A:** Masseter muscle - While the masseter muscle is involved in the movement of the mandible, it is primarily responsible for elevating the mandible, not lateral movement.
**Option B:** Temporalis muscle - The temporalis muscle is also involved in elevating the mandible, but it is not directly involved in lateral movement.
**Option C:** Digastric muscle - The digastric muscle is involved in depressing the mandible, not lateral movement.

**Clinical Pearl / High-Yield Fact**
The lateral pterygoid muscle is the primary muscle responsible for lateral movement of the jaw, and its dysfunction can lead to temporomandibular joint (TMJ) disorders.

**Correct Answer: C. Lateral pterygoid muscle.**