Explanation:

Capsella is a flowering plant that belongs to the Brassicaceae family. It is an angiosperm because it possesses fruit.

Angiosperms

Angiosperms are plants that produce flowers and fruits. They are commonly known as flowering plants. Angiosperms are characterized by the presence of flowers, which are reproductive structures that contain male and female gametes. They also possess fruits, which are mature ovaries that contain seeds.

Seed

A seed is a reproductive structure that contains an embryo, which is capable of developing into a new plant. Seeds are produced by angiosperms and gymnosperms. They are dispersed by various mechanisms such as wind, water, and animals.

Pollen grain

Pollen grains are male gametophytes that are produced by the anthers of flowers. They are transferred to the stigma of the same or a different flower to fertilize the female gametophyte. Pollen grains are produced by angiosperms and gymnosperms.

Vascular tissue

Vascular tissue is a specialized tissue that transports water, minerals, and nutrients throughout the plant. It consists of xylem and phloem. Xylem transports water and minerals from the roots to the leaves, while phloem transports sugars and other organic compounds from the leaves to the rest of the plant.

Fruit

A fruit is a mature ovary that contains seeds. It is produced by angiosperms. Fruits are important for seed dispersal and are consumed by animals and humans for their nutritional value. They come in various forms such as berries, drupes, and pods.

Conclusion:

Capsella is an angiosperm because it produces flowers and fruits. Fruits are the mature ovaries that contain seeds. Therefore, option D is the correct answer.