Forceful expiration results from a forceful contraction of diaphragm.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The statement claims that forceful expiration results from the forceful contraction of the diaphragm. We need to determine if this statement is true or false.

2. **Defining Forceful Expiration**: Forceful expiration refers to the process of actively expelling air from the lungs beyond normal breathing. This is typically done during activities such as vigorous exercise or when trying to clear the lungs.

3. **Role of the Diaphragm**: The diaphragm is a dome-shaped muscle that separates the thoracic cavity from the abdominal cavity. During normal expiration, the diaphragm relaxes and moves upward, allowing air to exit the lungs. However, during forceful expiration, the diaphragm does not contract forcefully; instead, it relaxes.

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