Which of the following tissues, cells, or structures in flowering plants is a part of the sporophyte generation and therefore diploid? - generative nucleus - sperm -synergid -cell of endosperm - cell of an integument

When flowering plants reproduce by sexual reproduction, they form seeds contained into fruits. The fruit is derived from the maturation of the flower's ovary (female part) after fertilization.

A mature seed contains three generations:

a diploid embryo (the new sporophyte),
The embryo is surrounded by haploid female gametophyte tissue that supplies nutrition
All the above structure is in turn surrounded by the seed coat (diploid parental sporophyte tissue). The seed coat is produced by integument cells to protect the embryo during its development and before its can germinate. As it is produce by it parental plant, its ploidy level diploid.

In contrast, the generative nucleus and sperm cell are part of male gametophyte (pollen grain) and therefore haploids. Synergid cell is part of embryo sac, therefore belongs to female gametophyte and thus being haploid. Finally, cell of endosperm is usually derived from the fusion between a sperm cell and one of the two female gametes present within the embryo sac, thus being triploid.