Kelly hears an economist argue that organized labor lowers businesses' productivity. What is the most likely basis for the economist's argument?
A. Union workers do not put forth as much effort as non-union
workers.
B. Union organizing historically involved manufacturing jobs.
C. Union workers do not receive employee benefits.
D. Union pay tends to be higher than non-union pay for similar jobs.

D. Union pay tends to be higher than non-union pay for similar jobs.

Explanation:

Labor unions are always advocating for higher wages for their members.  As a result, organized labor is always paid higher wages than the market rates. The exorbitant wages and benefits that unionized workers get make the per-unit output of labor expensive. A company with union workers will pay higher wages per hour or per unit produced than a business that pays as per the market rates.