During the process of inhalation, the muscles of the ribs and the diaphragm expand.

Explanation

### Step-by-Step Solution

1. **Understanding Inhalation**: Inhalation is the process of taking air into the lungs. It involves the movement of the diaphragm and the rib cage.

2. **Role of the Diaphragm**: The diaphragm is a dome-shaped muscle located at the base of the thoracic cavity. During inhalation, the diaphragm contracts and moves downward. This contraction increases the volume of the thoracic cavity.

3. **Role of the Rib Muscles**: The intercostal muscles, which are located between the ribs, also play a crucial role. When these muscles contract, they lift the rib cage upwards and outwards, further increasing the volume of the thoracic cavity.

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