Answer:
b. discrimination
Step-by-step explanation:
Discrimination: In psychology, the term "discrimination" is described as an individual's capabilities of responding or perceiving differences among various stimuli. Discrimination is often considered as one of the most advanced sorts of learning as compared to generalization (capabilities of perceiving similarities). However, an organism can be trained for generalizing as well as discriminating.
In the question above, Mary’s treatment of Millie is best described as discrimination.