According to _____, the most important predictor of relationship success is having both partners feel that each is doing his or her "fair share."

A) social identity theory
B) social exchange theory
C) the investment model
D) the evolutionary approach

This statement aligns with social exchange theory, which suggests that individuals are motivated by self-interest and seek to maximize rewards and minimize costs in their relationships. In this case, both partners feeling that they are doing their fair share would be considered a reward, and feeling like one is not contributing as much as the other would be seen as a cost. Therefore, according to social exchange theory, this would be a key predictor of relationship success. Neither social identity theory, the investment model, nor the evolutionary approach specifically address the importance of perceiving fairness in relationships.