A V-shaped valley, like the one shown, is a narrow valley with steep sides that appear to form the shape of a "V." Which statement best explains how this type of valley is typically formed? A) They are formed by weak streams, slowly wearing away rock over time. B) They are formed by forceful streams, cutting down into rock over time. Eliminate C) They are formed by massive mountain glaciers slowly moving down slopes. D) They are formed by forceful winds moving between the walls of the valley.