Which quote from the source "Racial and Ethnic Disparities in Educational Attainment Persist in Rural America" best relays the central idea?
a) "... higher educational attainment is associated with higher median earnings, higher employment rates, and greater workforce opportunity."
b) "In rural areas of the country, ethnic and racial disparities persist in education..."
c) "In the United States, most of the population has completed high school, and a rising number have gone on to earn a college degree."
d) "... Blacks/African Americans had the largest decrease (20 percentage points) of rural individuals without a high school degree."