The World Bank's GNP per capita classification for low-income, middle-income and high income countries respectively is
a. less than $900, $900-$9,000 and more than $9,000.
b. less than $5,000, $5,000-$15,000 and more than $15,000.
c. less than $100, $100-$1,000 and more than $1000.
d. less than $50,000, $50,000-$150,000 and more than $150 000