An _________ is the sac-like structure with the fluid that surrounds the embryo.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the name of the sac-like structure that surrounds the embryo and is filled with fluid.

2. **Identifying the Structures**: In human reproduction, when an embryo develops, it is surrounded by several extra embryonic membranes. These membranes include the amnion, chorion, allantois, and yolk sac.

3. **Focusing on the Amnion**: Among these membranes, the amnion is specifically known for being a sac-like structure that contains a fluid. This fluid is called amniotic fluid.

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