Which of the following plants is known to assure seed setting even in the absence of pollinators?

The plant known to assure seed setting even in the absence of pollinators is Viola. This genus of flowering plants includes species that can reproduce through a process called cleistogamy, where flowers self-fertilize before opening. This unique adaptation allows Violas to produce seeds without the need for pollinators, ensuring successful reproduction even in conditions where pollinators might be scarce.

Cucumber, while it is a crop that can also produce seeds, typically relies on pollination for proper fruit and seed development. Similarly, lilies generally require pollinators, although some species may have adapted to self-pollination to a degree. Papaya plants are known for their dioecious nature, meaning they have separate male and female plants, which necessitates pollination by insects or wind for seed formation in female plants. Thus, compared to these other plants, Viola stands out for its ability to ensure seed setting independently of pollinator presence.