Which type of embryo sac is most common in angiosperms?

The correct answer is Option (2) → Monosporic with three sequential mitotic divisions

Meiosis of the megaspore mother cell gives four megaspores. In a majority of flowering plants only one megaspore is functional; the other three degenerate. An embryo sac formed from a single megaspore is called monosporic. Its nucleus then divides by mitosis three times in a row: 1 → 2 nuclei, 2 → 4 and 4 → 8. So the common embryo sac is monosporic and passes through three sequential mitotic divisions to reach the 8-nucleate stage.

Option (1) Tetrasporic with one mitotic stage of divisions — Incorrect. A tetrasporic embryo sac would use all four megaspores. The common type uses only one, and one division cannot give 8 nuclei.

Option (2) Monosporic with three sequential mitotic divisions — Correct. One functional megaspore and three free-nuclear mitotic divisions (2, 4, then 8 nuclei) form the typical embryo sac.

Option (3) Monosporic with two sequential mitotic divisions — Incorrect. Monosporic is right, but two divisions give only 4 nuclei. The mature embryo sac has 8.

Option (4) Bisporic with two sequential mitotic divisions — Incorrect. A bisporic embryo sac would come from two megaspores. In most flowering plants only one megaspore develops.

NCERT Extract:
Female Gametophyte – “In a majority of flowering plants, one of the megaspores is functional while the other three degenerate. Only the functional megaspore develops into the female gametophyte (embryo sac). This method of embryo sac formation from a single megaspore is termed monosporic development. … The nucleus of the functional megaspore divides mitotically to form two nuclei which move to the opposite poles, forming the 2-nucleate embryo sac. Two more sequential mitotic nuclear divisions result in the formation of the 4-nucleate and later the 8-nucleate stages of the embryo sac.”