In Robert Rescorla's Experiment, What Happened to the Group of Dogs

Multiple Choice

In Robert Rescorla's experiment, what happened to the group of dogs to whom a shock was consistently presented after a tone?

A) The group of dogs became immune to the shock.
B) The group of dogs became calm in the presence of the tone.
C) The group of dogs learned to show a playful response in the presence of the tone.
D) The group of dogs learned to show a fear response at the sound of the tone.