Which Statement About Animal Development Is True

Multiple Choice

Which statement about animal development is true?

A) Differentiation of cells into different cell types involves signaling molecules.
B) In frog embryos, β-catenin is necessary but not sufficient for the formation of the primary embryonic organizer.
C) Blastomeres are early embryonic cells that form during gastrulation.
D) The mouth of the sea urchin forms from the blastopore.
E) Cells migrate during the blastula stage.