The World's Economies Can Be Divided into Four Main Categories

The world's economies can be divided into four main categories according to their annual per-capita income levels: low-income, lower middle-income, upper middle-income and high-income economies. What category would Singapore falls under?

A) low-income
B) upper middle-income
C) high-income
D) lower middle-income
E) Singapore falls between low income and lower middle-income economies.