The correct option is C Uterus
An embryo develops from a zygote after sexual reproduction in organisms. The zygote undergoes mitosis division to form a mass of cells called blastula. This process is called as blastulation. Blastocyst includes an inner cell mass that carries out implantation of the embryo in the endometrium lining of the uterus. Thus, the process of blastulation starts in the uterus.