The structure which separates the thoracic cavity from abdominal cavity in mammals is ………….. .

Explanation

**Step-by-Step Solution:**

1. **Identify the Cavities**: Understand that mammals have two main body cavities: the thoracic cavity and the abdominal cavity. The thoracic cavity contains the lungs and is protected by the rib cage, while the abdominal cavity houses organs such as the stomach.

2. **Determine the Structure Separating the Cavities**: Recognize that there is a specific structure that separates these two cavities. This structure plays a crucial role in respiration and protects the organs in both cavities.

3. **Identify the Structure**: The structure that separates the thoracic cavity from the abdominal cavity in mammals is called the diaphragm.

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