Which of the following structures is responsible for protecting developing flowers?

The sepal plays a crucial role in protecting developing flowers, particularly in the early stages of development. It is usually located at the base of the flower and forms the outermost whorl of floral structures. Sepals are typically leaf-like and can serve multiple functions, including shielding the delicate flower bud from environmental factors such as mechanical injury and dehydration prior to blooming. Once the flower opens, the sepals often remain present at the base, continuing to offer some degree of support and protection for the other parts of the flower, such as petals, stamens, and carpels. This protective nature is essential for ensuring that the reproductive structures develop successfully, which is a key aspect of a plant's life cycle.

In contrast, the ovary is involved in reproduction but does not serve a protective function for the entire developing flower. The petals are primarily involved in attracting pollinators and do not contribute to protection during the bud stage. The stamen is the male reproductive part of a flower and is also not designed for the protection of developing structures. Therefore, the sepal is the correct choice for its protective role.