A、males. B、ethnic males. C、white males. D、women. C此题考查听细节的能力。题干中的“be used for comparison”与It is also used to com pare对应。

The wage gap is a statistical indicator often used as an index of the status of women’s earnings relative to men’s. It is also used to compare the earnings of other races and ethnicities to those of white males, a group generally not subject to race --or sex--based discrimination. The wage gap is expressed as a percentage (e. g. , in 2003, women earned 76% as much as men) and is calculated by dividing the median annual earnings for women by the median annual earnings for men.
    The Equal Pay Act was signed in 1963, making it illegal for employers to pay unequal wages to men and women who hold the same job and do the same work. At the time of the EPA’s passage, women earned just 58 cents for every dollar earned by men. By 2003, 40 years later, that rate had only increased to 76 cents, an improvement of less than half a penny a year. Minority women fare the worst. African-American women earn just 65 cents to every dollar earned by white men, and for Hispanic women that figure drops to merely 54 cents per dollar.
    If working women earned the same as men (those who work the same number of hours; have the same education, age, and union status; and live in the same region of the country), their annual family incomes would rise by $4,000 and poverty rates would be cut in half.