A Research Group Claims That They Have Discovered Microscopic Fossilized

Multiple Choice

A research group claims that they have discovered microscopic fossilized embryos,including some at the blastula stage,but other researchers are skeptical.Finally,one student develops a technique for splitting the embryos in half to reveal the substructure.Cutting open the first blastocyst embryo,the student is very excited."It is a blastula!" she shouts,"Look,you can see the ________ inside!"

A) granulosa cells
B) hollow blastocoel
C) archenteron
D) neural tube