Aid agencies estimated that approximately four million residents of required food aid in 2009. a. ethiopia b. greece c. cuba d. somalia

Using complete sentences, describe the central economic problem facing all humans. why does this require people to make choices? how can this result in opportunity costs?

Which country is currently the most populated country in the world? a. india b. china c. mongolia d. indonesia

17. the soil erosion pictured here is the result of what? a. harvesting renewable resources at a rate greater than the sustainable yield b. a mudslide caused by excessive rains c. harvesting renewable resources at a rate lower than the sustainable yield d. the transition between geologic eras and eons