Pollination is the process by which pollen grains are transferred from the male reproductive organ (anther) to the female reproductive organ (stigma) in plants. This transfer of pollen is essential for fertilization and subsequent seed production. While pollination can occur in various plant groups, the correct option in this case is 'C' - Angiosperms and gymnosperms.

Angiosperms and Gymnosperms:

- Angiosperms: Angiosperms are flowering plants that produce seeds enclosed within a protective structure called the ovary. They are the most diverse and advanced group of plants, comprising about 90% of all plant species. Examples of angiosperms include flowering trees, grasses, and garden plants.

- Gymnosperms: Gymnosperms are non-flowering plants that produce seeds exposed directly on the surface of specialized structures called cones. Unlike angiosperms, they lack true fruits and flowers. Gymnosperms include conifers (such as pines, spruces, and firs), cycads, ginkgoes, and gnetophytes.

Pollination in Angiosperms and Gymnosperms:

- Angiosperms: In angiosperms, pollination occurs through various mechanisms, including wind pollination, self-pollination, and insect or animal pollination. Wind-pollinated angiosperms produce large quantities of lightweight pollen grains that are easily carried by the wind. They have inconspicuous flowers with reduced or absent petals and produce abundant pollen. Examples of wind-pollinated angiosperms include grasses and many trees, such as oaks and birches. In contrast, insect or animal-pollinated angiosperms have showy flowers with attractive colors, fragrances, and nectar to attract pollinators like bees, butterflies, and birds. These flowers produce sticky or spiky pollen grains that adhere to the bodies of the pollinators, ensuring effective transfer between flowers.

- Gymnosperms: Unlike angiosperms, gymnosperms are primarily wind-pollinated. They produce large quantities of pollen grains that are light and small, enabling them to be easily dispersed by wind currents. Gymnosperms typically have cones, with male cones producing pollen and female cones containing ovules. When the wind-borne pollen grains land on the receptive surface of the female cone, pollination occurs. The pollen tube then grows from the pollen grain to the ovule, facilitating fertilization and seed development.

Conclusion:

Pollination occurs in both angiosperms and gymnosperms. While angiosperms employ a wider range of pollination strategies, including insect and animal pollination, gymnosperms primarily rely on wind pollination. Therefore, option 'C' - Angiosperms and gymnosperms is the correct answer.