**Core Concept**
The posterior belly of the digastric muscle is a superficial muscle in the neck that lies anterior to the sternocleidomastoid muscle. The structures lying deep to the posterior belly of the digastric muscle include the occipital artery, the lesser occipital nerve, and the posterior auricular artery, which are all important anatomical landmarks in the neck.

**Why the Correct Answer is Right**
The correct answer is related to the anatomical structures that lie deep to the posterior belly of the digastric muscle. The occipital artery and the lesser occipital nerve are two such structures. The occipital artery arises from the external carotid artery and supplies the scalp, while the lesser occipital nerve is a branch of the cervical plexus that provides sensory innervation to the skin of the posterior aspect of the scalp. The posterior auricular artery also arises from the external carotid artery and supplies the skin of the posterior aspect of the ear.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the occipital artery is indeed one of the structures lying deep to the posterior belly of the digastric muscle.

**Option B:** This option is incorrect because the lesser occipital nerve is also one of the structures lying deep to the posterior belly of the digastric muscle.

**Option C:** This option is incorrect because the posterior auricular artery is indeed one of the structures lying deep to the posterior belly of the digastric muscle.

**Clinical Pearl / High-Yield Fact**
It's worth noting that the digastric muscle is a unique muscle in the neck that has two bellies: an anterior belly and a posterior belly. The posterior belly is innervated by the facial nerve, while the anterior belly is innervated by the mylohyoid nerve, which is a branch of the mandibular division of the trigeminal nerve.

**Correct Answer: A.**