Which of the Following Correctly Explains Why Wages Are Higher

Which of the following correctly explains why wages are higher in the United States than in less developed countries?

A) The number of hours worked per worker in the U.S.is higher than it is in less developed countries.
B) The aggregate labor supply curve in the U.S.is highly inelastic.
C) The output produced by each worker is higher in the U.S.than in less developed countries.
D) The substitution effect of a wage increase is greater for the U.S.residents than it is for residents of less developed countries.