What are four factors which influence the ways languages change?

Influence by other languages
isolation
poetry
influence of social or religious groups
age of the person using language
educational system

As the boys sleep, military airplanes battle fiercely above the island. none of the boys sees the explosions and flashes in the clouds because the twins sam and eric, who were supposed to watch the signal fire, have fallen asleep. during the battle, a parachutist drifts down from the sky onto the island, dead.