Answer:
The answer is d. Equity theory.
Step-by-step explanation:
As the name implies, this theory is based on the idea that workers are motivated by fairness, and will adjust their performance according to what they consider as fair.
This strategy, when done well, ensures that workers feel in a comfortable environment; on the other hand if, for instance, a worker notices a peer that makes more money for the same job, he might decrease his/her performance and do less work.