The nucleus formed by the fusion of a male gamete and two nuclei of the central cell is called the primary endosperm nucleus (PEN). This process is known as triple fusion. Therefore, the primary endosperm nucleus is triploid.
A zygote is formed by the fusion of haploid male and female gamete. Thus, it will be diploid.
During the embryo sac formation, the haploid cells form the antipodal cells and synergids. Thus, the pair that is mismatched is an option (d).