Which of the following is a prevalent free-floating weed?

Waterhyacinth is indeed a prevalent free-floating weed. This aquatic plant is characterized by its buoyant, broad leaves and striking purple flowers. It thrives in warm waters, forming dense mats on the surface of ponds, lakes, and waterways. Its rapid growth and ability to reproduce vegetatively contribute to its prolific spread, which can lead to serious ecological and navigational impacts.

In contrast, the other choices represent submerged or emergent aquatic plants rather than free-floating species. Common elodea, Eurasian watermilfoil, and curlyleaf pondweed are rooted in the substrate and grow underwater. Their growth habits and ecological roles differ significantly from those of waterhyacinth, which remains afloat and tends to dominate water surfaces, leading to problems such as diminished light penetration and oxygen depletion in the water body.