Which of the following is true regarding the per person income of the world during the past 1000 years? a. The world's income per person has approximately doubled during the past 1000 years and most of that growth has occurred since 1900. b. The world's income per person changed very little during the 800 years prior to 1813, but it has increased by nearly tenfold during the past 200 years. c. The world's income per person has grown steadily during the past 1000 years. d. The world's per person income grew at an annual rate of more than 2 percent during 1000-1813, but the annual growth rate has declined as the population increased during the past 200 years.]