Answer:
B) the sounds of the mother moving around
Explanation:
Discriminative stimulus: In psychology, the term discriminative stimulus refers to an antecedent stimulus that possesses stimulus control over a particular behaviour because that behaviour was reinforced in the presence of that specific stimulus in past.
In other words, the discriminative stimulus is referred to as a stimulus in whose presence a particular response is being reinforced.
In the question above, the discriminative stimulus is the sounds of the mother moving around.