**Core Concept**
The cerebellum is a critical brain region involved in motor coordination, balance, and learning. Its output cells play a crucial role in transmitting information from the cerebellar cortex to other brain regions, ultimately influencing motor function.

**Why the Correct Answer is Right**
The output cells of the cerebellum are called Purkinje cells. These large, branching neurons receive excitatory inputs from the mossy fibers and climbing fibers, and they project their axons to the deep cerebellar nuclei (DCN). The DCN, in turn, sends output signals to other brain regions, including the thalamus and the motor cortex, to modulate motor function. Purkinje cells use GABA as their neurotransmitter, which is an inhibitory neurotransmitter, to regulate the activity of the DCN.

**Why Each Wrong Option is Incorrect**
**Option A:** is incorrect because basket cells are inhibitory interneurons that synapse onto Purkinje cells, but they are not output cells of the cerebellum.
**Option B:** is incorrect because stellate cells are also inhibitory interneurons that synapse onto Purkinje cells, but they are not the primary output cells of the cerebellum.
**Option C:** is incorrect because granule cells are the most numerous neurons in the cerebellum, but they are not the output cells; they transmit excitatory inputs from the mossy fibers to the Purkinje cells.

**Clinical Pearl / High-Yield Fact**
Damage to the cerebellum or its output cells, such as Purkinje cells, can lead to ataxia, a disorder of motor coordination and balance. This highlights the importance of the cerebellum's output cells in regulating motor function.

**Correct Answer: C. Granule cells are the primary input cells of the cerebellum, and Purkinje cells are the primary output cells.**