The correct answer is horse and zebra.
Horse and Zebra are members of class a Mammalia. A mammal develops from one celled zygote, which is a fusion product of an ovum or egg and a sperm. After fertilization the zygote undergoes cleavage, increasing the number of cells. After repetitive division blastocyst are formed. The blastocyst is characterized by a group of cells, called the inner cell mass or embryo blast) and the trophoblast.
