The cerebrum is the largest part of the brain, accounting for about 85% of its mass. It is located at the top of the brain and is divided into two hemispheres, the left and right hemispheres. The cerebrum is responsible for higher-order functions such as thought, memory, language, and consciousness.
The thalamus is a small, egg-shaped structure located in the center of the brain. It is responsible for relaying sensory information from the body to the cerebrum.
The medulla oblongata is a small, cylindrical structure located at the base of the brain. It is responsible for controlling involuntary functions such as breathing, heart rate, and blood pressure.
The cerebellum is a large, wrinkled structure located at the back of the brain. It is responsible for coordinating movement, balance, and posture.
Therefore, the correct answer is D. Cerebrum.