During Gastrulation, Three Different Cell Layers Become Apparent

Multiple Choice

During gastrulation, three different cell layers become apparent. One of these is the ectoderm (ecto = outer, dermis = skin) . Immediately within the ectoderm is the mesoderm. As ecto = outer, and endo = inner, what would be the term given to the cell layer folded within the invaginating vegetal plate?

A) Endocarp
B) Endoderm
C) Endoform
D) Endochyma
E) All of the options listed are incorrect