According to one study, between 1979 and 2012, the share of all household income accruing to the top percentile of U.S. households rose from 10.0% to 22.5%.

According to the same study,the earnings gap between college-educated and high school-educated workers rose over the same time period.

Between 1979 and 2012, the median earnings gap between a college-educated two-earner husband-wife family and a high school-educated two-earner husband-wife family increased by about __________ per year.

A. $1,000

B. $27,000

C. $47,000

D. $7,000