Which condition features motor neuron degeneration?

Amyotrophic lateral sclerosis (ALS) is the condition that specifically features motor neuron degeneration. This neurodegenerative condition primarily affects the motor neurons, which are vital for controlling voluntary muscle movements. As these neurons degenerate and die, the brain loses the ability to initiate and control muscle movements, leading to muscle weakness, atrophy, and eventually paralysis.

In contrast, Alzheimer's disease is characterized by the degeneration of neurons involved in memory and cognitive functions, rather than motor neuron degeneration. Parkinson's disease primarily affects dopaminergic neurons in the brain, leading to motor symptoms such as tremors and rigidity, but does not involve the motor neurons in the same way that ALS does. Multiple sclerosis involves damage to the myelin sheath covering nerve fibers, disrupting communication between the brain and the body, but it does not exclusively cause degeneration of motor neurons like ALS does. Therefore, the unique and defining feature of ALS is the degeneration of motor neurons, making it the correct choice in this case.