The correct anwser would be D high mountains. The Indus and Ganges rivers are known for the beutiul high mountains.
D) remains of dead organisms
yes, they do come from plants and animals but when they're dead.
They have a characteristic U shape, with steep, straight sides and a flat or rounded bottom (by contrast, valleys carved by rivers tend to be V-shaped in cross-section). Glaciated valleys are formed when a glacier travels across and down a slope, carving the valley by the action of scouring.
