Apomictic seeds develop in certain plants due to:

The correct option is D all of the above.
Apomixis is a phenomenon which results in the formation of seeds without fertilisation.

There are several ways by which apomictic seeds can develop in the plant.

1. Endoreplication: It is the replication of DNA (nuclear genome) without the subsequent completion of mitosis and cytokinesis. This results in the duplication of the genetic material in the cell.
Endoreplication of the haploid genetic material transforms the haploid egg cell into a diploid egg cell. This diploid egg cell then develops into an embryo without fertilisation.

2. The nucellar cells start dividing and protrude into the embryo sac and develop into embryos without fertilisation.

3. In another method, the diploid egg cell is produced without reduction division. This diploid egg cell develops into an embryo without fertilisation.

All the above said methods result in the formation of apomictic seeds.