This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Development period- week 1,2,3,4, Subject name: Anatomy
Which process establishes the three definitive germ layers? 
Select and explain. 
A. Neurulation, B. Gastrulation, C. Craniocaudal folding, D. Lateral folding
B: Gastrulation
Answer: B: Gastrulation 
Explanation: Gastrulation - three primary germ layers from epiblast during week 3 of development i.e dorsal ectoderm, middle mesoderm, ventral endoderm. Neurulation is the process by which neuroectoderm forms the neural plate, which eventually folds to form the neural tube.