Answer:
Option B
Step-by-step explanation:
The Reciprocity Norm:
This rule of social psychology says that, in many of the social situations whenever a person or some one does a favor for a person than that person feels obligated to payback that favor to that person.
Thus in the case of Mrs. Chanski and her children, the reciprocity norm applies where she felt obligated to return the favor by buying the cookies.