The correct option is A Zygote
After fertilization, the zygote is formed which is diploid in nature. The zygote undergoes cleavage divisions (rapid mitosis) to form a 16-celled stage, called as morula. The morula then undergoes blastulation to form a blastula and blastula undergoes gastrulation to form a gastrula.
Thus, the zyogte is the only structure, that undergoes cleavage.
Hence, the correct answer is option A.