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
Gravity??? Honestly don’t know.
The world is improving energy efficiency and vehicle fuel economy and also increasing wind and solar power.
It depends on the map. There should be a key indicated.
