What does hierarchical society mean?

Based on this map, which statement about africa’s economic activity is most accurate? a) coastal countries are all members of opec b) economic development is more common with opec nations c) coastal countries have more access to productive resources d) economic development is more common above the sahara desert

Find the coordinates of a if b(-9,-10) is the midpoint of ac and c has the coordinates of (-1,9)

The process by which liquid water changes into water vapour is called what ?