Assertion (A) : An embryo sac in angiosperm is 7 celled and 8 nucleated.

Reason (R) : Embryo sac contains 2 synergids, 3 antipodal cells, 1 egg cell and 1 central cell and all the cells contain one nucleus except the central cell that contains 2 polar nuclei.

Assertion is true. Embryo sac is a 7-celled and 8-nucleate structure that is formed by the process of megasporogenesis and megagametogenesis.

Reason is also true. The embryo sac contains three antipodal cells at the chalazal end, two synergids at the micropylar end, one egg cell, and one central cell in the middle. The central cell contains two polar nuclei that are positioned in the center of the embryo sac and are surrounded by the cytoplasm.

Embryo sac in angiosperms is 7-celled and 8-nucleated, as stated in assertion (A). The reason (R) provided explains the cell and nucleus distribution within the embryo sac.