During the past 50 years, the world's population experienced

a. substantial increases in per capita GDP for 20 percent while the remaining 80 percent remained in abject poverty

b. substantial increases in per capita GDP for 50 percent while the remaining 50 percent remained in abject poverty

c. declining per capita GDP

d. substantial increases in per capita GDP for 5 billion while the remaining one billion remained in abject poverty

e. substantial increases in per capita GDP for one billion while the remaining 5 billion remained in abject poverty