Which plant is known for having extensive rhizomes that produce tubers?

The correct choice is the River Bulrush, as it is well-known for its extensive rhizomatic growth, which produces tubers. This type of plant structure allows the River Bulrush to propagate effectively in aquatic environments. The rhizomes serve as a means for the plant to store nutrients and energy, enabling it to survive adverse conditions and facilitating vegetative reproduction. The ability to produce tubers is particularly beneficial as it allows the plant to establish itself in various waterbody conditions and can help in stabilizing sediment in aquatic habitats.

In contrast, while other plants listed may have different forms of growth or reproductive strategies, they do not possess the same rhizomatous and tuberous characteristics as River Bulrush. The unique adaptations of River Bulrush to both its environment and reproductive strategy set it apart as the correct answer in this context.