The seven-celled and eight nucleated female gametophytes of an angiospermic plant is produced as a result of divisions of functional megaspore

The correct option is A Three mitotic

The megaspore produces two nuclei by the first mitotic division which moves to opposite poles and forms 2- nucleate embryo sac. Further second mitosis produces 4 nucleate and then the third mitosis produces 8 nucleate stage of the embryo sac. After 8 nucleate stage, the cell wall is laid down and typical embryo sac is formed. Among 8, 6 nuclei are organised into cells, remaining two are in the large central cell. Out of 6, 3 are at the micropylar end, 2 cells are synergids while one is egg cell. Other 3 are at the chalazal base called as antipodal cells. So, the angiosperm embryo sac is 8 nucleated and 7 celled.

Thus, the correct answer is option A.