This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Anatomy
The 3 embryonic germ layers: ectoderm, mesoderm and endoderm are derived from: 
Select and explain. 
A. Epiblast only, B. Ectoderm from epiblast; mesoderm and endoderm from hypoblast, C. Ectoderm and mesoderm from epiblast; endoderm from hypoblast, D. Hypoblast only
A: Epiblast only
Answer: A: Epiblast only 
Explanation: All three embryonic germ layers (ectoderm, mesoderm and endoderm) are derived from the epiblast only. The hypoblast contributes to the development of the extraembryonic mesoderm and yolk sac and plays a key role in signaling to establish axial patterning in the embryo itself