The correct option is D Secondary nucleus
In the case of double fertilization, which occurs in angiosperms, the primary nucleus fused with one of the nuclei of male gamete and produces zygote and secondary nucleus fuses with another nucleus of the male gametes and forms endosperm. Endosperm provides nourishment for the developing embryo. The other male gamete which enters the embryo sac fuses with the haploid egg and forms the embryo. Thus, the correct answer is option D.