In angiosperms, functional megaspore develops into
Endosperm
Pollen sac
Embryo sac
Ovule
The megaspore mother cell of the megasporangium divides meiotically to create four megaspores. wherein the embryo sac is formed from a single functioning megaspore. The other three are corrupt. The female gametophyte is contained in this embryo sac. Megasporogenesis and megagametogenesis are two distinct processes that result in the creation of an embryo.
The final answer is In an angiosperm, a functional megaspore develops into an embryo sac.