How did ocean exploration start in the 1440s and 1500s?

What enabled the drastic increase in us troop development to vietnam between 1964 and 1965?

Which number shows the location of italy?

This photo shows an early mesoamerican structure, specifically from the zapotec culture. what was this structure most likely used for? a.creating terraces for farm fieldsb.practicing religious ceremoniesc.playing a ball game with stone hoopsd.protecting a city from invading armies