Answer:
The answer is D. Stimulus generalization.
Step-by-step explanation:
In classic conditioning theory, stimulus generalization is the concept used to describe the process in which the conditioned response prsents itself with other stimulus that are similar to the conditioned stimulus. This concept was first used in the study called Little Albert experiment.
In this case, Diana's conditioned response was fear, and it appeared after she was conditioned to fear the nighbor's budgie bird, the bird was the conditioned stimulus. However, she also began to fear other types of birds, in fact she is afraid of all birds. Her conditioned response extended to other similar stimulus.