Reasons for the Growing Income Inequality in the United States

Reasons for the growing income inequality in the United States since 1975 include the following, except

A) a shift in labor demand toward highly skilled and better-educated workers.
B) the entrance of larger numbers of less-experienced, less-skilled workers into the workforce.
C) an increase in the number of households headed by single or divorced women.
D) the decline of unionism in the U.S. workforce.