Concept:The upper course of a river has a steep gradient and fast-flowing water, causing mainly vertical erosion that creates features like waterfalls.
Explanation:In the upper course, the river flows swiftly down steep slopes.
This gives the river high energy, so it cuts downward into the landscape through vertical erosion.
When a river flows over alternating layers of hard and soft rock, the softer rock erodes more quickly.
This undercuts the hard rock, leaving a ledge that collapses, forming a waterfall.
Ox-bow lakes are formed later when meanders are cut off in the lower course.
Deltas and levees are depositional features found near the river mouth in the lower course.
Thus, among the options, only a waterfall is typical of the upper course.
Answer:B. Waterfall