Social exchange theory is based on the idea that

A) people exchange psychological defense mechanisms during social interaction
B) communities must have viable economies in order to be healthy
C) sharing resources is a fundamental component of successful living
D) people calculate rewards and costs in deciding how to act with respect to other people

Social exchange theory posits that people engage in social interactions with the goal of maximizing rewards and minimizing costs. In other words, individuals weigh the benefits and drawbacks of a given action or relationship before deciding whether to pursue it or not. This approach assumes that human behavior is rational and self-interested, and emphasizes the importance of reciprocity in relationships. Therefore, choice D is the best answer.