This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Embryology, Subject name: Anatomy
Gastrulation occurs at which week of gestation: 
Select and explain. 
A. 1 week, B. 5 week, C. 3 week, D. 10 week
C: 3 week
Answer: C: 3 week 
Explanation: Ans. C. 3 weekThe gastrulation is the most characteristic event occurring during the third week of gestation because it forms the three germ layers that form all the tissues and organs of the body. The process of formation of three germ layers is called gastrulation.