Scenario II The Following Model of Emotion Is Based on the Following

Scenario II
The following model of emotion is based on the following work:
LeDoux, J. E. (2000) . Emotion circuits in the brain. Annual Review of Neuroscience, 23, 155-184.
Psychologist Joseph LeDoux tracked the neural mechanisms underlying the fear response in rats. Rats were exposed to the sound of a tone followed by an electric shock. After a few tone-shock pairings, the tone elicited species-typical defense behaviors such as freezing and increased sympathetic activity (e.g., an increase in heart rate) . Using this fear-conditioning paradigm, LeDoux argued for the existence of both fast and slow neural pathways underlying the fear response. A particular brain structure (arbitrary labeled "A") simultaneously routes sensory information to structures "B" and "C." In the fast pathway, information is routed to structure "C"-a limbic structure long known to be involved in emotional experiences such as fear-where it is rapidly assessed. If appraised as a threat, structure "C" activates the fear response. In the slow pathway, information travels to other structures in the brain (labeled "B") involved in planning and more advanced decision-making. The results of the appraisal by structure "B" is used by structure "C" to continue or terminate the fear response.
-(Scenario II) Which of these constitutes an operational definition of a learned fear response?

A) the A-B-C pathway with the structures correctly identified
B) ten pairings of the tone and shock, with a 5-milliamp shock occurring 1 second after each tone presentation
C) an increase in heart rate elicited by the tone alone as measured by an implantable telemetry device
D) freezing behavior that occurs after the shock, as measured by locomotor counts in the pressure-sensitive floor of a testing apparatus