Which plant appears as small, green floating objects that may or may not have roots?

Duckweed is the correct choice because it is characterized by its small, green floating bodies that can vary in size and often have tiny root systems that hang down into the water. This plant typically forms extensive mats on the surface of ponds and lakes, providing important habitat for various aquatic organisms. Duckweed plays a significant role in freshwater ecosystems and is known for its rapid growth, which can sometimes lead to challenges in managing its populations.

In contrast, cattails are tall, emergent plants typically found at the edges of wetlands, and they do not float on the surface but grow from the water or soil. Purple loosestrife is a tall flowering plant that grows in wetlands but is rooted in the substrate rather than floating. Waterlilies, while also common in aquatic environments, are recognized by their larger leaves and flowers that typically float on the water’s surface but are supported by long stems anchored in the substrate, which distinguishes them from the smaller floating nature of duckweed.