Why is the thalamus referred to as the gateway to the cortex?

Why is the thalamus referred to as the gateway to the cortex?
 
  a. Motor outputs generated in the cerebral cortex are funneled first through the thalamus, which then sends inputs to the motor neurons.
  b. Input from most of our sensory systems travels first to the thalamus, which then funnels the information to the cerebral cortex.
  c. Motor outputs generated in the thalamus are funneled first through the cerebral cortex, which then sends inputs to the motor neurons.
  d. Input from most of our sensory systems travels first to the cerebral cortex, which then funnels the information to the thalamus.