In eukaryotic life cycle Embryonic development starts after fertilization when egg or zygote is formed. After the formation of zygote it undergoes successive Mitotic division proceeds through segmentation to form the multicellular embryo.
Through segmentation blastocyst and gastrula are formed and then subsequently three embryonic layers are formed that is ectoderm, mesoderm and endoderm. these layers helps in the formation of organs.
Therefore the Correct Answer is A. Mitosis