Answer:
(a) CS
Step-by-step explanation:
Based on the information provided within the question it can be said that in this scenario Susan's voice would be considered to be the Conditioned Stimulus. This term refers to a previously neutral stimulus, that is later used in combination with an unconditioned stimulus in order to produce a conditioned response. Which in this scenario she is combining her voice with the name of the cat to produce the conditioned response of him coming to her.