…………………………… sphincter prevents regurgitation of food from the stomach.

Explanation

**Step-by-Step Solution:**

1. **Understanding Regurgitation**: Regurgitation refers to the act of food that has been swallowed coming back up into the mouth. This can happen if there is a failure in the mechanisms that keep food in the stomach.

2. **Identifying the Structure**: The question asks about a sphincter that prevents this regurgitation. A sphincter is a circular muscle that constricts or dilates to control the passage of substances.

3. **Location of the Sphincter**: The relevant sphincter in this context is located between the esophagus and the stomach. The esophagus is the tube that carries food from the mouth to the stomach.

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