Question

Anne has been observing human embryos in different stages. She wants to study the gastrula phase. How will she find it?

Answer 1

Take a look at this picture:
http://upload.wikimedia.org/wikipedia/commons/d/d9/Blastula.png

We can see that the GASTRULATION phase is where we can see a GASTRULA,
with THREE different layers:

1. Ectoderm
2. Mesoderm
3. Endoderm

Anne just needs to look for these three layers.
When she sees them, she'll know that the embryo is in the Gastrula phase.

Answer 2

Btw I took this from http://openstudy.com/study#/updates/5141f02ee4b0f08cbdc990ef so no one thinks I'm copying :)

Answer 3

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Answer 4

B