What part of a flowering plant does a seed typically contain?

A seed typically contains an embryo with a protective coat and stored food, which is essential for the seed's development into a new plant. This structure is critical because the embryo represents the future plant, while the protective coat safeguards it from environmental hazards and pathogens during its dormant phase. The stored food within the seed acts as a nutrition source for the embryo as it begins to grow and establish itself after germination.

The other components like the flower or stem are necessary for reproduction and overall plant structure but are not found within the seed itself. Similarly, leaves and roots, while integral to the plant's lifecycle and function, do not form part of the seed. Pollen and nectar are related to the reproductive processes of flowering plants but are not included in seeds. Thus, option B accurately describes what a seed encompasses, highlighting its role in the life cycle of flowering plants.