<span>Aside from the fact that 1920s films were black and white and some movies in the 1930s had color, sound was a major difference.</span>
"<span>c. Native American raids on work camps" would be the best option from the list, but the primary and most severe hardship was the rough terrain, which featured rivers, mountains, etc.</span>
Probably because any activities related to environment protection require a change of mentality and habits and participation of everyone in order to be fruitful.
