What kind of landscape or terrain would pools like cenotes become very important as sources of groundwater?

Air pollution: “combustion results in gases such as nitrogen oxides, nitrogen dioxide and particulates. the main causes of air pollution include transport, domestic combustion and industrial processes. pollutants from these sources can cause problems in the immediate vicinity and a distance away.”

Ones bigger then than the other

Largely uneconomic because they provide little profit or food surplusi think so