6. Which supercontinents were present on Earth at the beginning of the Cretaceous period?
O A. Rodinia
O B. Laurussia and Gondwana
O C. Laurasia and Gondwana
O D. Pangaea

The most common economic system in the world is aclosed economy.command economy.mixed market economy.traditional economy.

Name the two rivers that run through the fertile crescent. how were the rivers both positive and negative to societies of the fertile crescent?

Match your vocabulary word to its definition. 1. emigration 2. immigration 3. migration 4. overpopulation 5. sustainable development 6. under population 7. unsustainable development 8. urbanization the movement from one place to another the number of people exceeds the available natural resources in an area leaving one's homeland to settle in a new place the increase in the population of a city the movement of people to a new country the ability to meet current needs without reducing the ability to meet future needs resources being used up at a faster rate than they can be replenished birth rate insufficient to replace the existing population