The correct option is C endosperm
Of the two sperm cells entering the embryo sac, one sperm fertilizes the egg cell, forming a diploid zygote; the other sperm fuses with the two polar nuclei, forming a triploid cell (primary endosperm nucleus) that develops into the endosperm. Together, these two fertilisation events in angiosperms are known as double fertilisation. Cotyledon is an embryonic leaf in seed-bearing plants, one or more of which are the first leaves to appear from a germinating seed.