Kathy's Heart Rate Increases Every Time She Goes Down a Certain

Multiple Choice

Kathy's heart rate increases every time she goes down a certain hallway at school. The boy that she likes has a locker in that hallway, and he often stands beside his locker and talks with friends. In the preceding scenario, which of the following is best described as the conditioned stimulus?

A) Kathy's heart rate
B) The hallway where the boy's locker is located
C) The boy's locker
D) The boy standing with friends