Human Embryos Differ from Bird Embryos in That

Human embryos differ from bird embryos in that:

A) bird embryos have an extra membrane, the allantois, that is not found in human embryos.
B) human embryos have no yolk sac.
C) human embryos have a yolk sac, but it contains no yolk.
D) human embryos do not develop into a primitive streak stage.
E) bird embryos develop a very different body structure than the adult.