Final answer:
The area where a river fans out as it flows into a larger body of water is called a delta, which is a landform created by the deposition of sediment carried by the river as it loses speed.
Step-by-step explanation:
A delta is an often triangular-shaped section of land formed as the waters of a river slow down and split into many channels as they deposit sand and silt that has been carried downriver. When a river reaches a larger body of water, such as a lake or ocean, the decrease in current speed causes the river to spread out and deposit the material it has transported, creating a delta.
Notable examples of large rivers that form significant deltas include the Nile River in Africa, the Amazon River in South America, and the Mississippi River in North America. A gamma is not a geographical term related to rivers, a beta does not define a river feature, and a cataract is a place in a river where there’s a significant drop, such as a waterfall or rapids, not where a river fans out. Therefore, the direct answer to this question about the area where a river fans out as it flows into a larger body of water is indeed a delta.