Question

the fluid - filled sac that contains and protects the embryo inside the placenta is called?
amniotic sac
fetal sac
umbilical sac
placental sac

Explanation:

In the context of human development (a topic in Biology, a subfield of Natural Science), the amniotic sac is the fluid - filled structure that encloses and protects the embryo/fetus. The other options ("fetal sac", "umbilical sac", "placental sac") are not the correct anatomical terms for this structure.

Answer:

A. amniotic sac