Answer:
A. Haploid (n)
Explanation:
Conifers do not exhibit double fertilization that forms triploid (3n) endosperm in flowering plants.
Endosperm in conifers develops from the haploid cell of female gametophyte before fertilization. Since the endosperm is formed by the mitotic divisions in the haploid cell (n) of female gametophyte, it is haploid (n) in nature.