Since the 1970s, Families Whose Income Lies in the Middle

Since the 1970s, families whose income lies in the middle of the income distribution (of all U.S. families) have kept up with the cost of living primarily by

A) having husbands take second jobs.
B) relying on parental "gifts" for purchases such as down payments on houses.
C) taking advantage of changes in the tax structure for married couples.
D) having wives take jobs outside the home.