Okay, let's tackle this question. The patient has sudden double vision and his right eye is turned medially at rest. The key here is to figure out which cranial nerve or muscle is involved.

Double vision, or diplopia, often points to a cranial nerve issue affecting eye movement. The medial deviation suggests that the lateral rectus muscle isn't working. The lateral rectus is responsible for abducting the eye, so if it's paralyzed, the eye would turn inward. The lateral rectus is innervated by the abducens nerve (CN VI). So, a lesion in CN VI would cause the eye to deviate medially.

Wait, but there's another possibility. If the medial rectus is overacting, that could also cause medial deviation. However, the medial rectus is innervated by the oculomotor nerve (CN III). So if CN III is affected, it's more about ptosis, pupillary issues, and maybe the eye being down and out. But the question says the eye is turned medially when at rest. If CN III is paralyzed, the eye would be in a downward and outward position because the medial rectus is still active? Hmm, no. Wait, if the oculomotor nerve is paralyzed, the eye can't move up, down, or medially. The lateral rectus (CN VI) and superior oblique (CN IV) would be the remaining muscles. So the eye might be in an abducted position? Not sure. Let me think again.

The medial deviation when at rest points to the lateral rectus not working. So the abducens nerve (CN VI) is the main one here. So the structures involved would be the abducens nerve and the lateral rectus muscle. The answer is probably involving the lateral rectus and CN VI. The other options might be other nerves or muscles. Let me check the options again. The question lists options A to D, but they're not provided. But the correct answer is supposed to be about CN VI and lateral rectus. So the correct answer would be the structures related to those. The other options might include other nerves like CN III or IV, or other muscles like medial rectus. But since the eye is turned medially, it's the lateral rectus that's paralyzed. So the correct answer is the lateral rectus and CN VI. The key here is the lateral rectus and abducens nerve. The clinical pearl is that CN VI palsy leads to medial deviation and horizontal diplopia, worse on abduction.

**Core Concept**
This question assesses understanding of cranial nerve innervation of extraocular muscles. The **abducens nerve (CN VI)** innervates the **lateral rectus**, which abducts the eye. Paralysis of this nerve leads to medial deviation due to unopposed action of the medial rectus.

**Why the Correct Answer is Right**
The patient’s right eye is medially deviated at rest, indicating **lateral rectus palsy**. Since the lateral rectus is innervated by CN VI, a lesion in this nerve prevents abduction, causing the eye to drift medially. Double vision occurs because the affected eye cannot align with the unaffected eye during horizontal gaze.

**Why Each Wrong Option is Incorrect**
**Option A:** If the oculomotor nerve (CN III

✓ Correct Answer: C. Lateral rectus and abducent nerve