The right option is; D. more snow falls then melts
Glaciers can only form when more snow falls then melts.
Glaciers are large thickened body of ice that is formed due to the compression of fallen snow over a long period of time. Glaciers are formed when snow falls and the snow is positioned in one area for a long time which then melts and changes into ice. Glaciers have the ability to flow under its own mass, and it covers about 10 percent of the world’s land area.
Social science, any branch of academic study or science that deals with sociology, psychology, political science, and economics. Most historians, however, consider history as one of the humanities.