The answers are A) ectoderm and B) endoderm.
Fertilization is a fusion of male and female gametes which leads to the formation of a zygote. The zygote undergoes mitosis and transforms into a single-layered blastula. Gastrulation is a transformation of the blastula into a two-layer or three-layer gastrula. Cnidarians are a diploblastic animal because their gastrula has only two layers - endoderm and ectoderm.
