(a) Per Capita Income
The World Bank classifies countries and prepares its development report primarily on the basis of per capita income.
The textbook (Chapter 1) clearly states that the World Bank uses per capita income as the main criterion for classifying countries. In contrast, the UNDP's Human Development Report uses income along with health and education indicators. Examiners expect students to distinguish between the two — World Bank = per capita income; UNDP = HDI (income + health + education).