The fluid filled membrane that cushions the developing fetus and protects it from mechanical shock is the

Explanation

The amnion encloses the amniotic fluid in which the fetus floats, spreading any pressure evenly, keeping the temperature steady and allowing free movement of the limbs. The chorion is the outer membrane that contributes the fetal part of the placenta, so it has a nutritive rather than a protective role. In humans the yolk sac and allantois are much reduced compared with birds and reptiles.