One Difference Between Early Development in Humans and in Xenopus

Multiple Choice

One difference between early development in humans and in Xenopus is that

A) in humans,there is no formation of the blastula;in Xenopus,the blastula is a critical stage in early embryogenesis.
B) in humans,blastocysts implant into the uterine wall;there is no implantation in Xenopus.
C) in humans,gastrulation is delayed as the egg moves along the fallopian tube;in Xenopus,gastrulation takes place immediately after blastula formation.
D) in humans,the yolk sac is much smaller than that seen in Xenopus.
E) in humans,neurulation occurs immediately after cleavage;in Xenopus,neurulation is delayed until after gastrulation.