Which of the Following Is an Example of a Compensating

Which of the following is an example of a compensating differential?

A) paying workers with more years of experience higher wages than workers with fewer years of experience, all else equal
B) paying workers who work on the night shift higher wages than workers who work the day shift, all else equal
C) paying accountants who have passed the Certified Public Accountant exam higher wages than accountants who have not passed it, all else equal
D) paying workers with PhDs higher wages than workers with BAs, all else equal