Final answer:
The "relay station" of the brain is the thalamus, which serves as the central hub for most sensory and motor signals, routing them to regions of the cerebral cortex.
Step-by-step explanation:
The portion of the brain referred to as the "relay station" is the thalamus. The thalamus is a critical structure in the forebrain that functions as a hub for sensory and motor signals. With the exception of the olfactory system, all sensory signals are first transmitted to the thalamus. This includes inputs from the visual system, auditory system, somatosensory system, and the taste system. Once in the thalamus, the signals are then routed to the appropriate regions of the cerebral cortex for further processing. Therefore, the correct answer to the multiple-choice question is d. thalamus.