**Core Concept**
The hypoglossal nerve (CN XII) is a motor nerve that innervates the muscles of the tongue, controlling its movements such as protrusion, retraction, and lateral deviation. Complete unilateral damage to the hypoglossal nerve would result in weakness or paralysis of the affected side of the tongue.

**Why the Correct Answer is Right**
In a patient with complete unilateral damage to the hypoglossal nerve, the tongue on the affected side would be deviated towards the side of the lesion due to the unopposed action of the muscles on the contralateral side. This is because the genioglossus muscle, which is the primary muscle responsible for tongue protrusion, is innervated by the hypoglossal nerve. The deviation of the tongue is a classic clinical sign of hypoglossal nerve damage.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the tongue would indeed be weak or paralyzed on the affected side, leading to difficulties in speaking, swallowing, and eating.

**Option B:** This option is incorrect because the tongue would be deviated towards the side of the lesion, not away from it.

**Option C:** This option is incorrect because the muscles of the tongue on the affected side would be weak or paralyzed, leading to atrophy and fasciculations.

**Option D:** This option is incorrect because the hypoglossal nerve does not have any sensory fibers; it is a purely motor nerve.

**Clinical Pearl / High-Yield Fact**
A classic clinical sign of hypoglossal nerve damage is the "tongue protrusion test," where the patient is asked to protrude the tongue and the examiner observes the direction of deviation. This test can help diagnose unilateral hypoglossal nerve damage.

**Correct Answer:** D. The hypoglossal nerve is a purely motor nerve and does not have any sensory fibers.