Answer:
D. higher-order conditioning had occurred
Explanation:
Higher Order Conditioning is a classic Pavlov conditioning term that refers to a situation in which a previously neutral stimulus is paired with a conditioned stimulus to produce the same conditioned response as the conditioned stimulus.
In the case of the experiment conducted by John Watson and Rosalie Rayner, baby Albert was subjected to a situation in the presence of a stimulus that was previously neutral (the presence of a white rat that did not generate fear in the baby), paired with a conditioned stimulus ( the loud sound that frightened the baby) so that the baby would associate the sound with the hairy animal's presence and have the same response to both stimuli.