Answer;
The amnion
Explanation;
-The amnion is a tough, thin membrane that surrounds a developing fetus in mammals, reptiles, and birds. It is the first of the three cavities (amnion, chorion and yolk sac) in the embryo and is formed on 8 dpc.
-In the human body, the amnion is the first of three cavities, including the chorion and yolk sac, that work together to keep the developing fetus nourished and protected.
-The amnion provides a protective environment in which the fetus' temperature is regulated and protects the fetus from friction caused by the mother's movements.
I think the best answer is D. It is thought that advances such as agriculture, literacy, and urbanization have not been accompanied by additional increases in brain size because the physiological cost of a bigger brain exceeds its benefit. The brain requires a lot of nutrients to function. Having a bigger brain would cost a lot rather than benefiting from it.
