After implantation, what begins to occur? What does it result in terms of the structure of the embryo now?
a) Gastrulation; formation of germ layers; formation of the neural tube
b) Neurulation; formation of blastocoel; formation of the yolk sac
c) Gastrulation; formation of blastocoel; formation of the trophoblast
d) Neurulation; formation of the germ layers; formation of the chorion