What characteristic defines Angiosperms?

The defining characteristic of angiosperms is that they are plants that produce seeds enclosed within a fruit. This unique feature sets angiosperms apart from other plant groups, such as gymnosperms, which have seeds that are not enclosed in fruits. The presence of flowers and fruits plays a crucial role in the reproductive process of angiosperms, facilitating pollination by various agents, including insects and wind, and promoting the dispersal of seeds through various mechanisms associated with fruit.

In contrast, the other choices do not accurately represent angiosperms. Asexual reproduction is characteristic of many plant species but is not a defining trait of angiosperms. Furthermore, angiosperms are not exclusively aquatic; they are found in a variety of ecosystems, both terrestrial and aquatic. Lastly, angiosperms are distinctly characterized by the presence of seeds, so the notion of having no seeds directly contradicts the defining feature of this group. Thus, the characteristics of seed production in fruit highlight the evolutionary advancements of angiosperms, making them one of the most diverse and widespread groups of plants.