The least dense layers of the earth are found at the-a. outer edgeb. inside the middlec. inner core

I believe the answer is A; outer edge.

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.”

The war began as a fight between mayans and the landowners of the country. the main causes of the guatemalan civil war was started by the greed of the united fruit company, the fear of communism, and the racism toward the  mayan  people.