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

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.