In this scenario, hearing the word "goodbye" is the: conditioned stimulus.
Classical conditioning can be defined as a learning process through which two (2) stimuli are paired together repeatedly. Thus, it is a learning process which typically involves pairing two (2) stimuli, so as to help an individual anticipate an event that he or she has a reaction for.
In classical conditioning, the two (2) stimuli that are paired repeatedly include the following:
A conditioned stimulus refers to a neutral stimulus that eventually triggers a conditioned response, after it is repeatedly paired (associated) with the unconditioned stimulus.
In this example, hearing the word "goodbye" is the conditioned stimulus because it made Susie's husband to elicit a response, which is flinching.
Read more on conditioned stimulus here: https://brainly.com/question/24868138