**Core Concept**
A waddling gait is a type of abnormal gait characterized by a broad-based, unsteady gait pattern, often resulting from weakness or paralysis of the lower limb muscles. This condition is typically associated with disorders affecting the motor control and coordination of the lower limbs.

**Why the Correct Answer is Right**
Waddling gait is commonly seen in patients with **Friedreich's ataxia**, a rare genetic disorder that affects the nervous system and causes progressive damage to the spinal cord, peripheral nerves, and the cerebellum. This damage leads to impaired motor control, coordination, and balance, ultimately resulting in a waddling gait. The pathophysiology involves **degeneration of the large sensory and motor neurons in the spinal cord** and **dysfunction of the cerebellum**, leading to loss of coordination and balance.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because **Hemiplegia**, a condition characterized by weakness or paralysis of one side of the body, typically results in a hemiparetic gait, not a waddling gait.
**Option B:** This option is incorrect because **Parkinson's disease** typically results in a shuffling gait, not a waddling gait.
**Option C:** This option is incorrect because **Multiple sclerosis** can result in a variety of gait disturbances, but a waddling gait is not a typical presentation.

**Clinical Pearl / High-Yield Fact**
It's essential to distinguish between different types of gait disturbances in patients with neurological disorders, as each type can provide valuable clues about the underlying pathology.

**Correct Answer: D. Friedreich's ataxia**