The correct answer is option 3, that is, blastomeres.
Explanation:
A kind of cell formed by cleavage of the zygote post-fertilization is called a blastomere, it is an important constituent of blastula formation. The formation of blastomere starts instantaneously post-fertilization and is carried through the initial week of the development of embryo. The division of zygote after fertilization is regarded as the first mitotic outcome of the fertilized oocyte. These mitotic divisions take place spontaneously and lead to a grouping of cells known as blastomeres.
