To Your Chagrin,you and Your Labmate Have Discovered That You

Multiple Choice

To your chagrin,you and your labmate have discovered that you both labeled your petri dishes "A","B",and "C".How can you distinguish your sea urchin gastrula embryos from her frog gastrula embryos?

A) Unlike frogs,sea urchins are deuterostomes,which form the anus first and the mouth second.
B) Sea urchin cells migrate inside to form the archenteron,whereas in frogs proliferation of dividing cells from the dorsal lip populate the inside of the embryo.
C) Sea urchins have relatively yolk-poor eggs with similar animal and vegetal poles,whereas frogs have large amounts of yolk distinguishing the vegetal pole from the animal pole.
D) Frogs have an animal pole and vegetal pole,whereas urchins have only a vegetal pole.