Which of the following defines a stream?

A stream is defined as a body of concentrated flowing water that moves through a natural channel. This definition captures the essence of what characterizes a stream: its continuous movement and the specific physical structure—a natural channel—through which the water flows. Streams can vary in size and flow rate but are unified by the fundamental characteristic of being a flowing waterway.

The other options describe different types of water bodies or water features. Standing water, for instance, refers to water that is not flowing, such as lakes or ponds, which fundamentally differs from the dynamic nature of streams. Wetlands are areas where water covers the soil or is present at or near the surface, which may include streams but do not define them specifically. An artificial waterway, like a canal, is typically man-made, while streams are naturally occurring. Thus, the definition provided in the correct choice distinctly captures the natural flow and structure that defines a stream.