**Core Concept**
The sixth cranial nerve, also known as the abducens nerve, is responsible for controlling the lateral rectus muscle, which abducts the eye. A left-sided sixth nerve palsy would result in weakness or paralysis of this muscle, leading to an inability to move the left eye outward.

**Why the Correct Answer is Right**
In the case of left-sided sixth nerve palsy, the affected individual would experience difficulty moving their left eye laterally, resulting in **esotropia**, a type of strabismus characterized by inward turning of the eye. This is because the lateral rectus muscle, which is responsible for outward movement, is weakened. The individual may also experience diplopia (double vision) due to the misalignment of the eyes.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the outcome of left-sided sixth nerve palsy. The affected individual would not experience upward gaze difficulties, as the sixth nerve is not responsible for upward movement.

**Option B:** This option is incorrect because it does not accurately describe the outcome of left-sided sixth nerve palsy. The affected individual would not experience downward gaze difficulties, as the sixth nerve is not responsible for downward movement.

**Option C:** This option is incorrect because it does not accurately describe the outcome of left-sided sixth nerve palsy. The affected individual would not experience difficulty moving their eye upward and outward, as the sixth nerve is not responsible for upward movement.

**Clinical Pearl / High-Yield Fact**
The sixth nerve is unique in that it has a long intracranial course, which makes it susceptible to compression or damage from tumors, aneurysms, or other intracranial pathology. This is why sixth nerve palsy can be a valuable indicator of underlying intracranial disease.

**Correct Answer: C. Esotropia.**