(a) Waterfall: occurs at the upper course of a river, occurs as a result of erosion, a resistant hard rock is left to form an obstacle, the protruding obstacle now causes the river to rumble down from a higher to lower ground, may be formed when a river plunges down the edge of a plateau, when a fault-line scarp lies across a river.
(b) Delta:

A feature of the lower course of a river/or at the mouth of a river.
Formed as a result of deposition of sediments at the lower course of a river.
Rate of deposition faster than rate of removal of silt at the coast slow rate of flow of the river.
Here the river divides into several channels called distributaries shallow depth of water along the coast.
The distributaries cut through the deposits before finally flowing into the sea

(c) Inselbergs: are isolated mountains formed as a result of intrusion of magma into the earth's crust and resisted erosion when all other surroundings were eroded, exposed by differential erosions by water or wind.