Answer: B — High Per Capita Income
A developed country is characterised by high per capita income, high literacy rate, low infant mortality rate, and high net attendance ratio.
The passage directly states that per capita income is a key measure used to classify developed countries (World Bank criterion). The other options — high IMR, low literacy rate, low net attendance ratio — are characteristics of underdeveloped/developing countries, as shown in Table 1.4 (e.g., Bihar has low literacy and high IMR). Eliminate wrong options by recalling that developed = high income, low IMR, high literacy.