Answer:
A. Blastocyst.
Explanation:
As a result of fertilization, a diploid zygote is formed. The zygote rapidly divides into multiple cells without increasing in size. The repetitive mitotic division is called cleavage. The daughter multiple cells rearranged to form a hollow ball called the blastula.
In the next stage of embryonic development is formation of the blastocyst. The cells within the blastula arrange themselves in two layers, the inner cell mass or embryoblast and the outer trophoblast.
The inner cell mass forms the embryo proper and the trophoblast takes part in the formation of the placenta and provides nutrition to the developing embryo.
