The correct option is C Pollen grains
The pollen grains represent the male gametophytes in flowering plants (angiosperms).
The gametophyte is the sexual phase in the life cycle of plants that produces haploid gametes. The gametophyte in angiosperms is highly reduced.
Anther consists of microsporangia that develop into pollen sacs. Sporogenous tissue occupies the centre of each microsporangium in a young anther. The cells of sporogenous tissue are called pollen mother cells (PMC). They are diploid cells that undergo meiotic division to form microspore tetrads. As the anther matures, the microspores of microspore tetrad dissociate and develop into pollen grains.
Pollen grains are haploid and represent the male gametophytic generation.
Megaspores are produced inside the ovules. Megaspores develop into female gametophytes.