## Core Concept
The horizontal semicircular canal is part of the **vestibular system** in the inner ear, which plays a crucial role in maintaining balance and eye movements. Stimulation of this canal activates the **vestibulo-ocular reflex (VOR)**, leading to nystagmus, a rhythmic movement of the eyes.

## Why the Correct Answer is Right
The horizontal semicircular canal is oriented in the plane of rotation that would cause the head to move from side to side. When this canal is stimulated, it activates the **ampullary nerve**, which sends signals to the brain that are interpreted as rotation. The brain then coordinates an eye movement in the opposite direction of the rotation to maintain focus, resulting in nystagmus. Specifically, stimulation of the horizontal semicircular canal causes a **torsional (rotational) nystagmus** with the **fast phase away from the stimulated ear** and the **slow phase towards the stimulated ear**.

## Why Each Wrong Option is Incorrect
- **Option A:** Incorrect because it does not accurately describe the direction of nystagmus caused by horizontal semicircular canal stimulation.
- **Option B:** Incorrect because it inaccurately represents the direction of nystagmus; the actual direction is related to the stimulated ear and the type of canal.
- **Option D:** Incorrect as it does not correctly specify the direction of nystagmus associated with stimulation of the horizontal semicircular canal.

## Clinical Pearl / High-Yield Fact
A key point to remember is the **mnemonic COWS** (Cold Opposite, Warm Same), which helps determine the direction of nystagmus in response to caloric testing of the vestibular system. However, for rotational stimulation like that of the horizontal semicircular canal, the fast phase of nystagmus is **away from the stimulated side**.

## Correct Answer: C.