Which of the following is an example of a flowing water freshwater ecosystem?

A flowing water freshwater ecosystem is characterized by water that moves continuously in a specific direction. Rivers exemplify this type of ecosystem as they involve the movement of water along a defined channel, typically from higher elevations to lower elevations, eventually flowing into larger bodies of water such as lakes or seas. This continuous flow influences the physical and biological characteristics of the ecosystem, supporting unique communities of organisms adapted to dynamic water conditions.

In contrast, lakes and ponds are examples of standing water ecosystems where water does not flow in a significant current, allowing for different ecological dynamics. Wetlands can include both standing and flowing water, but they are generally defined by their saturated soils and waterlogged conditions rather than the movement of water. Hence, rivers distinctly represent flowing freshwater ecosystems among the provided options.