Final answer:
The cerebrum is the largest part of the human brain, responsible for higher-order functions like speech and problem-solving.
So, the correct answer is a.
Step-by-step explanation:
The largest part of the human brain is the cerebrum. It sits atop the brainstem and is responsible for a variety of complex functions that we are consciously aware of, such as problem-solving, speech, and voluntary movements. The cerebrum includes the cerebral cortex, which is the folded surface colloquially referred to as gray matter. It is involved in processing sensory input, controlling motor functions, and enabling cognitive abilities like memory and reasoning.
The cerebrum is further subdivided into lobes, each associated with different functions; for example, the frontal lobe is concerned with abstract thought, problem-solving, and planning. The cerebellum, though smaller, also plays a critical role in body position, coordination, balance, and fine motor control. Meanwhile, the brainstem, including the medulla, is vital for maintaining life-sustaining autonomic functions such as breathing and heart rate.
So, the correct answer is a) Cerebellum.