**Core Concept**
The posterior border of the hyoglossus muscle is a significant anatomical landmark in the neck, and several structures pass deep to it as they course through the neck. These structures include nerves, vessels, and other muscles that play crucial roles in various functions, including swallowing, speech, and facial movements.

**Why the Correct Answer is Right**
The structures passing deep to the posterior border of the hyoglossus muscle from above to downwards include:
* The hypoglossal nerve (CN XII) is the twelfth cranial nerve, which innervates the muscles of the tongue, including the hyoglossus. It passes deep to the posterior border of the hyoglossus muscle to reach the tongue.
* The lingual artery, a branch of the external carotid artery, supplies the tongue and passes deep to the posterior border of the hyoglossus muscle.
* The lingual vein, which drains the tongue, also passes deep to the posterior border of the hyoglossus muscle.
* The glossopharyngeal nerve (CN IX) is another cranial nerve that passes through the neck and can be considered below the hypoglossal nerve in this anatomical context.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is blank, so it's impossible to provide an explanation for it.
**Option B:** This option is also blank, so it's impossible to provide an explanation for it.
**Option C:** This option is blank, so it's impossible to provide an explanation for it.
**Option D:** This option is blank, so it's impossible to provide an explanation for it.

**Clinical Pearl / High-Yield Fact**
When dissecting the neck, it's essential to identify the posterior border of the hyoglossus muscle and the structures passing deep to it. The hypoglossal nerve is particularly prone to injury during surgical procedures in this area, which can result in weakness or paralysis of the tongue.

**Correct Answer:**
Correct Answer: C.