Which plant reproduces by division and is commonly found in quiet water?

The correct choice is duckweed, which is a small floating aquatic plant that commonly reproduces through a process called vegetative reproduction, or division. In this method, a single plant can form new individuals by splitting or creating new shoots from its parent, allowing it to spread rapidly across bodies of quiet water. This ability to reproduce swiftly can lead to dense mats that cover water surfaces, providing habitat and food for various aquatic organisms.

In contrast, while Vallisneria americana (eelgrass) can also reproduce vegetatively, it is primarily rooted in sediment and typically grows in more dynamic environments rather than the quiet water where duckweed thrives. Water lilies, while they do reproduce by division as well, tend to have a different growth style; they maintain large, floating leaves stemming from substantial root systems that anchor them to the bottom. Wild celery typically relies more on seed production for reproduction, particularly in more flowing waters. Each of these plants has unique life cycles and habitats that differentiate them from duckweed, making it the most fitting answer for the given question.