Concept:The upper course of a river has steep slopes and intense downward erosion.
Explanation:In the upper course, the river flows rapidly down a steep gradient.
This strong downward cutting deepens the river valley, forming narrow, steep-sided valleys.
A gorge is exactly such a deep, narrow valley with rocky walls.
Levees, ox-bow lakes, and deltas are not found here.
They are features of the lower course or the river mouth.
Answer:B. Gorge