Answer:
The USA became involved in Vietnam because it feared the spread of communism. The USA were unable to defeat the Vietcong and were met with growing opposition to the war back home.
this is the only one I can answer, I'm sorry. I hope this helps though
Minerals, organic matter, water and air.
Lack of economic development!!! i hope that helps you
Natural elements typically erode ancient ( and all ) buildings and structures overtime. That and an increasing amount of tourist attraction also doesn’t help the decaying... well everything. An article from the guardian supports this and even says that last year the EU threatened to remove the funding of the Great Pompeii Project which conserves and restores this ancient site.
