30 POINTS!!!!!!!!!!!1
Which of the following lists the events occurring during development in the correct sequence?
A. Placenta formation; gastrulation; differentiation of tissue layers; chorion formation
B. Chorion formation; placenta formation; gastrulation; differentiation of tissue layers
C. Differentiation of tissue layers; gastrulation; placenta formation; chorion formation
D. Gastrulation; differentiation of tissue layers; chorion formation; placenta formation
