Infant mortality in the United States is higher among ____ families than in ____ families, in part because ____

a. middle-SES; low-SES; middle-SES mothers are more likely to live in rural parts of the country
b. middle-SES; high-SES; middle-SES fathers are more likely to be absent from the family
c. high-SES; low-SES; high-SES mothers are not likely to consume fluoride in their drinking water
d. low-SES; high-SES; low-SES mothers are less likely to receive prenatal care

Answer: D