Final answer:
The letter D on the diagram represents the Cerebellum, which is responsible for balance, coordination, movement, and motor skills. The correct answer is D. Cerebellum.
Step-by-step explanation:
The cerebellum is a structure located at the back of the brain stem and is often referred to as the 'little brain.' It plays a crucial role in controlling balance, coordination, movement, and motor skills. Additionally, the cerebellum is involved in procedural memory, which is the memory associated with learning and performing tasks.
Based on the information provided in the references, the pons, medulla oblongata, and thalamus are all parts of the hindbrain, while the cerebellum is a separate structure that connects to the pons.