Answer: (A) The reciprocity norm.
Explanation:
The reciprocity norm is basically refers to the expectation from other person that they respond more favorably and return benefit for the benefits.
We can also describe the reciprocity norm as if we are doing some good and beneficial action to the one individual person then we also expect the same respond from that person.
In the reciprocity norm, the action is in either positive or negative way. We can also say that we repay to other person who has done for you and it is important for building and also maintaining the relationship with another person.
Therefore, Option (A) is correct.