Which area of the economy benefited from the policies of the harding administration?
A) labor unions
B) foreign governments
C) domestic businesses
or
D) agricultural producers ???

Pretty much everybody. Harding reduced the Federal budget by half, and reduced the national debt by one third. He cut tax rates for every income group. His policies, largely overseen by his ingenious Secretary of the Treasury Andrew Mellon, led to one of the biggest 20th century economic booms. From the Wikipedia article: "The combined declines in unemployment and inflation (later known as the Misery Index) were among the sharpest in U.S. history. Wages, profits, and productivity all made substantial gains during the 1920s."
So maybe the best answer is C. But on the other hand, Harding intervened in the Great Railroad Strike of 1922 in an attempt, ultimately successful, to change the standard 12-hour workday to an 8-hour workday, a longstanding goal of labor leaders.