Angiosperms

The embryo sac, also known as the female gametophyte, is the structure within the ovule of an angiosperm that contains the egg cell and other cells involved in fertilization and seed development.

The mature embryo sac of angiosperms is commonly referred to as the "7-celled, 8-nucleate" structure. It consists of:

Three antipodal cells at one end,

Two synergids located near the egg cell,

A central cell with two polar nuclei,

The egg cell itself.

Therefore, the correct answer is (3) 8 nucleated 7 celled structure.

The ovule is the structure within the ovary of a flower that contains the female reproductive cells. It consists of various parts, including the megasporangium, which is the structure that houses the megaspore mother cell.

The megasporangium is responsible for producing and protecting the megaspore mother cell. The megaspore mother cell then undergoes meiosis, resulting in the formation of megaspores.

Therefore, the correct answer is (B) Megasporangium.