Which of the following structure is not supported by in complete cartilaginous rings.

Options

A. A) Trachea
B. B) Secondary bronchi
C. C) Terminal bronchioles
D. D) Primary bronchi

Answer

To solve the question "Which of the following structures is not supported by incomplete cartilaginous rings?", we need to analyze the respiratory structures and their support systems.

### Step-by-Step Solution:

1. **Understand the Structure of the Respiratory Tract**:
- The respiratory tract includes various structures such as the trachea, bronchi, and bronchioles.

2. **Identify the Role of Cartilaginous Rings**:
- In the respiratory system, incomplete cartilaginous rings are primarily found in the trachea and the primary and secondary bronchi. These rings provide structural support to prevent collapse during breathing.

3. **Examine the Structures**:
- **Trachea**: Supported by incomplete cartilaginous rings.
- **Primary Bronchi**: Supported by incomplete cartilaginous rings.
- **Secondary Bronchi**: Supported by incomplete cartilaginous rings.
- **Terminal Bronchioles**: These are the smallest branches of the bronchi and do not have cartilaginous support.

4. **Determine the Answer**:
- Since terminal bronchioles do not have incomplete cartilaginous rings, they are the structure that is not supported by these rings. Therefore, the correct answer is the terminal bronchioles.

### Final Answer:
The structure that is not supported by incomplete cartilaginous rings is the **terminal bronchioles**.

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