What are the two sources of energy that drive earth processes?

Long ago, people who lived in coastal north africa most often interacted with

Match the following terms and definitions a region in arkansas defined by the arkansas river in the western part of the state answer 1 a thoroughly dissected area with steep valley walls and narrow floors answer 2 a geographical region of a country or state answer 3 the friendly and generous reception and entertainment of guests, visitors, or strangers answer 4 the branch of knowledge concerned with the production, consumption, and transfer of wealth answer 5 statistical data relating to the population and particular groups within it answer 6 a mountain range in west central arkansas and southeastern oklahoma answer 7 travel for pleasure or business; also the theory and practice of touring, the business of attracting, accommodating, and entertaining tourists, and the business of operating tours answer 8 answer all parts of the question.

People keep spending additional units of a particular resource on a want until their marginal benefit is  decreasing withgreater thanless thannot affected by  their marginal cost.