The correct sequence of events during embryonic development isACleavage - differentiation - fertilization - gastrulationBDifferentiation - fertilization - gastrulation - cleavageCFertilization - cleavage - gastrulation - differentiationDFertilization - differentiation - cleavage - gastrulationEFertilization - gastrulation - differentiation - cleavage

Fertilization is fusion of male and female gamete. Immediately after fertilization, the embryological process that transforms single celled zygote into a hollow spherical multicellular blastula is referred to as cleavage. Cells of the blastula undergo gastrulation and form and segregate specific layers of tissue, called germ layers. The embryological strcture with three germ layers is termed as gastrula. These three germ layers then divide and differentiate into various organs. Correct sequence of events is fertilization, cleavage, gastrulation and differentiation.