Sites of respiration are bronchioles/alveoli.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks to identify the sites of respiration between bronchioles and alveoli.

2. **Defining Bronchioles**: Bronchioles are small airways that branch off from the bronchi and lead to the alveoli. They are primarily part of the conducting zone of the respiratory system, meaning their main function is to transport air to the lungs.

3. **Function of Bronchioles**: While bronchioles play a crucial role in the passage of air, they do not participate in the actual exchange of gases (oxygen and carbon dioxide).

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