Final answer:
A baby born with almost no brain can survive because the brainstem controls essential functions like breathing and heartbeat.
Step-by-step explanation:
The reason a baby born with almost no brain can survive for a couple of days is because the brainstem controls essential functions like breathing and heartbeat. The brainstem is the smallest part of the brain, located beneath the cerebrum, and it carries information between the cerebrum and spinal cord. It coordinates motor control signals and controls vital functions of the body, including alertness, breathing, blood pressure, heart rate, and digestion.