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
Which of the following is true regarding gastrulation - 
Select and explain. 
A. Establishes all the three germ layers, B. Occurs at the caudal end of the embryo prior to its cephalic end., C. Involves the hypoblastic cells of iinner cells mass, D. Usually occurs at 4 weeks
A: Establishes all the three germ layers
Answer: A: Establishes all the three germ layers 
Explanation: None