What are the most challenging sources of conflict and crisis in the 21st century?

Thank you!

answer; /// the correct answer is evidence of the olmec civilization has been found in southern american in a hot steamy forest, archaeologists have found earthen artifacts at several sites that were evidence of the olmec civilization. these   artifacts were mounds,courtyards and pyramids build of stones, also on top of the mounds were many monuments made of stone, some of these stone structures are very large, they weigh as much as 44

d

explanation:

because the vietnam war was fought in an especially brutal and untraditional way

whats the video? can u send a link?