Answer:
C.) equity theory.
Step-by-step explanation:
Equity theory -
The equity theory was given by J. Stacy Adams , back in the 1960's .
The theory of equity focus on the distribution of the resources , that whether their is equal distribution of resources or not , between the two people , is known as equity theory .
The equity measurement is done by comparing and contrasting the portion of the contributions and the benefits of both the person individually .
Hence , from the question ,
The manger is using equity theory .