After Establishing a Classically Conditioned Response to a Tone, an Experimenter

After establishing a classically conditioned response to a tone, an experimenter sets up a second trial using a new conditioned stimulus, a red light. He repeatedly pairs the new conditioned stimulus (the red light) with the conditioned stimulus from the first trial (the tone) . This procedure results in the conditioned response being elicited by the red light alone, even though it was never paired with the unconditioned stimulus. The experimental results demonstrate:

A) extinction.
B) higher order conditioning (second-order conditioning) .
C) learned helplessness.
D) the partial reinforcement effect.