What is the term for a mature and fertilized ovary of a flower?

The term for a mature and fertilized ovary of a flower is "fruit." Once the ovary is fertilized, it undergoes development to form fruit, which contains seeds that can grow into new plants. The fruit serves a critical role in the reproductive cycle of flowering plants by protecting the seeds and aiding in their dispersal.

Seeds are the structures that can develop into new plants, but they are found within the fruit. Petals are the often colorful parts of a flower that attract pollinators but are not involved in seed or fruit development. Nectar is a sugary fluid produced by flowers to attract pollinators but does not relate to the mature structure of the fertilized ovary. Thus, understanding the role of each component in plant reproduction clarifies why "fruit" is the correct answer to this question.