A typical Angiosperm embryo sac at maturity is 7-celled and 8-nucleate . While monosporic development (where the embryo sac develops from a single functional megaspore) is a common form of development mentioned in the sources , an 8-nucleated embryo sac can also be formed through bisporic or tetrasporic pathways depending on the species. Therefore, the correct answer is any of the above .