Look at the chart displaying the human development index (hdi) worldwide, which is linked to a high standard of living. based on what you know about developing and developed countries in the world, which sentence is correct?
a. as hdi increases, so does a nation's level of development.
b. a low hdi usually means that an economy is developed.
c. the hdi varies less in countries below the equator than those above the equator.
d. the hdi is highest in countries with command economies.