The main purpose of flowers is to produce seeds for reproduction (Option D is correct). Flowers also have other functions such as attracting pollinators and providing food and nectar for animals, but the primary purpose is reproduction.

The main purpose of flowers is to provide seeds.
- **Attracting Pollinators**: Flowers produce nectar, fragrance, and vibrant colors to attract pollinators such as bees, butterflies, birds, and other animals. These pollinators help in transferring pollen from one flower to another, leading to fertilization and the formation of seeds.
- **Reproduction**: The primary function of flowers is reproduction. Once pollination occurs, the flower's ovary develops into a fruit containing seeds. These seeds are vital for the continuation of the plant species.
- **Dispersal**: Seeds produced by flowers are dispersed through various methods such as wind, water, animals, or gravity. This dispersal helps in the survival and spread of plant species in different environments.
- **Genetic Variation**: Flowering plants produce seeds with genetic variations through processes like cross-pollination. This genetic diversity is crucial for the adaptation and evolution of plant species in changing environmental conditions.
- **Culinary and Medicinal Purposes**: Some flowers produce seeds that are edible and rich in nutrients. Additionally, certain seeds have medicinal properties and are used in traditional medicine practices.
In conclusion, while flowers serve aesthetic and ecological purposes, their primary function is to produce seeds for reproduction, genetic diversity, and the survival of plant species.