**Core Concept**
The dual nerve supply of muscles refers to the presence of two separate nerves that innervate the same muscle, often providing redundancy and facilitating recovery from nerve damage. This phenomenon is observed in various muscles throughout the body, particularly in the head and neck region.

**Why the Correct Answer is Right**
The correct answer is related to the anatomy and innervation of the muscles. Muscles with dual nerve supply often have a primary nerve supply that is responsible for voluntary movements, and a secondary nerve supply that provides involuntary or reflexive control. In some cases, the secondary nerve supply may be derived from a separate nerve or a branch of a nearby nerve.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because this muscle does have a dual nerve supply. The digastric muscle is innervated by the anterior belly of the digastric muscle from the mandibular division of the trigeminal nerve (cranial nerve V) and the posterior belly from the facial nerve (cranial nerve VII).
**Option B:** Incorrect because this muscle also has a dual nerve supply. The sternocleidomastoid muscle is innervated by the accessory nerve (cranial nerve XI) and the cervical plexus (C2-3).
**Option C:** Incorrect because this muscle has a dual nerve supply as well. The diaphragm is innervated by the phrenic nerve (C3-5) and the lower intercostal nerves (T6-12).

**Clinical Pearl / High-Yield Fact**
Muscles with dual nerve supply are more likely to recover from nerve damage, as the secondary nerve supply can compensate for the loss of function. This is particularly important in the head and neck region, where multiple nerves converge to innervate a single muscle.

**Correct Answer: D.**