Participants exposed to paired experiences of snakes and mild electric shock, then exhibited that they were experiencing palm sweat even when they only saw the pictures of the snakes. The snake photo was the __________

A) CS
B) US
C) CR
D) UR

Answer: A
Rationale: A conditioned stimulus (CS) is a once neutral stimulus that elicits a conditioned response (CR) because it has a history of being paired with an unconditioned stimulus (US). In this experiment by Ohman & Minkea (2001), the photos are the CS which eventually elicit the CR (palm sweat).