Final answer:
The neurons affected by Huntington's Disease are Medium-sized spiny projection neurons, which are integral to motor control. The correct option is D.
Step-by-step explanation:
The type of neurons that are primarily affected by Huntington's Disease (HD) are D) Medium-sized spiny projection neurons. These neurons are found in the central nervous system, specifically in the striatum, and they play a crucial role in motor control.
When these neurons degenerate, it leads to the motor symptoms associated with HD, such as involuntary movements, or chorea, and problems with muscle coordination.