## Core Concept
The cerebellar cortex primarily consists of inhibitory neurons, but there is a specific type of neuron that is excitatory. Understanding the types of neurons and their functions within the cerebellar cortex is crucial for comprehending its role in motor coordination and learning.

## Why the Correct Answer is Right
The cerebellar cortex contains several types of neurons, including Purkinje cells, granule cells, basket cells, stellate cells, and Golgi cells. Among these, **granule cells** are the only excitatory neurons. They receive input from mossy fibers and send excitatory signals to other neurons within the cerebellar cortex, such as Purkinje cells, through parallel fibers. This excitatory input from granule cells is fundamental for the processing of information within the cerebellum.

## Why Each Wrong Option is Incorrect
* **Option A:** This option is blank and does not provide a neuron type for evaluation.
* **Option B:** Similarly, this option lacks specific information about neuron types.
* **Option C:** This option also does not specify a neuron type.
* **Option D:** This option is incorrect because it does not accurately represent the excitatory neurons in the cerebellar cortex.

## Clinical Pearl / High-Yield Fact
A key point to remember is that **granule cells**, which are glutamatergic, are the only excitatory neurons in the cerebellar cortex. The majority of other neurons, including Purkinje cells, are inhibitory. This distinction is crucial for understanding cerebellar function and dysfunction.

## Correct Answer: D. Granule cells