The Linkage Between High Productivity and High Earnings Is Vitally

The linkage between high productivity and high earnings is vitally important because

A) it provides individuals with a strong incentive to develop skills and engage in activities that others value highly.
B) high productivity (a large output per hour worked) is the key to high living standards.
C) it brings the self-interest of individuals into harmony with economic progress.
D) all of the above are true.