Final answer:
Option (c), The thalamus is responsible for filtering sensory information and maintaining alertness by acting as a relay station and regulating wakefulness.
Step-by-step explanation:
The area of the brain that filters sensory information and helps to keep us alert is the thalamus. The thalamus acts as a relay station, processing and transmitting sensory information to the appropriate areas of the cerebral cortex, which is responsible for higher brain functions. Additionally, the thalamus plays a critical role in regulating wakefulness and alertness, which are essential for cognitive functions.