What characterizes a river compared to a stream?

The characteristic that defines a river, distinguishing it from a stream, is that a river typically flows over land carrying a larger volume of water. Rivers are generally wider and deeper than streams, which allows them to transport more water. This larger size enables rivers to support diverse ecosystems and often makes them significant for human use, such as for irrigation, transportation, and recreation.

In contrast to this definition, the other choices do not accurately characterize rivers. For example, rivers can be found in various terrains, including plains and valleys, not just mountainous areas. Additionally, rivers do have banks that define their boundaries, and they are not smaller in size; on the contrary, rivers are usually larger than streams.