Megaspores are produced from the megaspore mother cells after

In angiosperms,the embryo sac is formed from which of the following?

If a tetraploid plant contains $48$ chromosomes in its nucellus,then what is the number of chromosomes in the egg cell and in a synergid,respectively?

In angiosperms,the following events occur during megasporogenesis and megagametogenesis:
$(i)$ Differentiation of megaspore mother cells
$(ii)$ Meiosis of the megaspore mother cell
$(iii)$ Formation of a linear tetrad
$(iv)$ Mitotic division of the functional megaspore
$(v)$ Degeneration of $3$ megaspores
$(vi)$ Formation of embryo sac
$(vii)$ Fusion of polar nuclei
The correct sequence is:

Describe the structure of Megasporangium (ovule) with a diagram.

The megasporangium is equivalent to which structure in angiosperms?