What was crop rotation designed to do

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 of the activities listed below could limit global warming by slowing the increase in atmospheric carbon dioxide levels? view available hint(s) select all that apply. a. replacing fossil fuels with nuclear energy b. burning vegetation to clear land for agriculture c. limiting soil erosion so organic matter takes longer to decompose d. choosing a fuel-efficient car, or bicycling to school or work e. using more electrical appliances and cars f. cutting down forests to build houses

The earth is composed of three different chemical layers: core, mantle and crust. the formation of these layers was from a process called