Triple fusion results in the formation of:

The correct answer is Option (2) → Endosperm

A flowering plant shows double fertilisation. One male gamete fuses with the egg (syngamy) to form the diploid zygote. The other male gamete fuses with the two polar nuclei of the central cell. Three haploid nuclei fuse here, so this is called triple fusion. It gives a triploid primary endosperm nucleus.

(1) Embryo — Incorrect. The embryo develops from the zygote, which is formed by syngamy, not by triple fusion.

(2) Endosperm — Correct. The central cell, after triple fusion, becomes the primary endosperm cell and develops into the endosperm, the nutritive tissue for the embryo.

(3) Suspensor — Incorrect. It is a structure of the young embryo, so it belongs to the embryo that forms from the zygote.

(4) Egg — Incorrect. The egg is the female gamete, which is already present in the embryo sac before fertilisation. It takes part in syngamy.

NCERT Extract:
Double Fertilisation – “… Since two types of fusions, syngamy and triple fusion take place in an embryo sac the phenomenon is termed double fertilisation, an event unique to flowering plants. The central cell after triple fusion becomes the primary endosperm cell (PEC) and develops into the endosperm while the zygote develops into an embryo.”