**Core Concept**
The hypoglossal nerve (cranial nerve XII) is responsible for the motor innervation of the tongue, controlling its movements such as protrusion, retraction, and elevation. The genioglossus muscle, one of the extrinsic muscles of the tongue, plays a crucial role in tongue protrusion.

**Why the Correct Answer is Right**
When the patient protruded his tongue, it deviated to the right. This indicates that the left side of the tongue is being pulled to the right, suggesting that the left side of the tongue is weak. The hypoglossal nerve innervates the genioglossus muscle, which is responsible for protruding the tongue. Since the tongue deviated to the right, the left genioglossus muscle is likely weak, which is innervated by the left hypoglossal nerve. However, the question states that the tongue deviated to the right, implying that the right side of the tongue is stronger. Therefore, the right hypoglossal nerve and its associated muscle, the right genioglossus, are likely injured.

**Why Each Wrong Option is Incorrect**
**Option B:** The correct answer is not the left hypoglossal nerve and left genioglossus, as the tongue deviated to the right, not left.
**Option C:** The hyoglossus and styloglossus muscles are not responsible for tongue protrusion; they help in tongue retraction and elevation, respectively.
**Option D:** The geniohyoid muscle is involved in tongue elevation and laryngeal elevation, but not in tongue protrusion. The first cervical nerve is not directly related to tongue movements.

**Clinical Pearl / High-Yield Fact**
When testing cranial nerve function, it's essential to note the direction of deviation of the tongue during protrusion. A deviation to one side indicates weakness of the opposite side of the tongue, while a deviation to the midline suggests bilateral weakness.

**✓ Correct Answer: A. Right hypoglossal nerve and right genioglossus**