The correct option is C Hypothalamus
Mammals are homeotherms as they are capable of maintaining a constant body temperature irrespective of the surrounding environment.
The hypothalamus of the brain has centres for thermoregulation and plays a vital role in maintaining a constant body temperature.
The medulla oblongata contains centres which control respiration, cardiovascular reflexes and gastric secretions. Hence, it is involved in regulating the involuntary activities of the body.
The cerebrum contains sensory, motor and association areas. It has centers for intelligence, memory, reasoning, etc. A deep cleft divides the cerebrum longitudinally into two halves, which are termed as the left and right cerebral hemispheres. The hemispheres are connected by a tract of nerve fibres called corpus callosum.