(a) A
Country A has the highest GNI per capita ($12,578), highest life expectancy (76.4 years), and the best (lowest) HDI rank (73) among the given countries.
The question asks for all three criteria — high per capita income, high life expectancy, and high (i.e., numerically low/better) HDI rank. Scanning the table, Country A scores best on all three parameters simultaneously, making it the correct answer. Remember: a lower HDI rank number means a better position in human development.