Which of the following aquatic plants primarily uses rhizomes for reproduction?

Curly-leaf pondweed is the correct choice because it primarily reproduces through rhizomes, which are underground horizontal stems that allow the plant to spread and establish new growth. This method of reproduction is advantageous in aquatic environments, as it enables the plant to rapidly colonize areas and compete effectively for resources.

In contrast, watermilfoil primarily reproduces through fragmentation, where pieces of the plant can develop into new plants. Naiad uses both seeds and vegetative reproduction but is not primarily reliant on rhizomes. Bladderwort also reproduces through fragmentation and seeds, and while it can have rhizomes, it does not primarily rely on them as a method of reproduction. Understanding these characteristics helps in managing these plants effectively in aquatic environments.