Final answer:
The d) ovule, part of the flower's carpel, will enclose the endosperm after fertilization when it develops into a seed. The endosperm acts as a food reserve for the embryo inside the seed, which eventually grows into a new plant.
Step-by-step explanation:
In the process of plant reproduction, the flower part that will eventually enclose something with endosperm is the ovule (d). The ovule is located within the ovary of the flower's female reproductive structure, the carpel. After fertilization, the ovule develops into a seed containing the endosperm, which serves as a food reserve for the developing embryo. This is a critical step for seed development and subsequent growth into a new plant.
The formation of the seed includes the development of the seed coat, cotyledons, endosperm, and embryo. The endosperm is a nutritious tissue that provides energy and nutrients to the growing embryo. In angiosperms, the walls of the ovary thicken after fertilization to become the fruit, which encloses and protects the seed and ensures efficient dispersal.