Tracheal rings are `:-`

Options

A. Complete
B. Incomplete
C. Dorsally incomplete
D. Lateral incomplete

Answer

### Step-by-Step Solution:

1. **Understanding Tracheal Rings**: The tracheal rings are cartilaginous structures that provide support to the trachea, which is the windpipe that connects the larynx to the lungs.

2. **Structure of the Trachea**: The trachea is a tube that extends from the lower edge of the larynx to the upper part of the chest. It is essential for conducting air to and from the lungs.

3. **Shape of the Rings**: The tracheal rings are shaped like a horseshoe or the letter "C". This shape is crucial for maintaining the structure of the trachea while allowing flexibility.

4. **Arrangement of the Rings**: These cartilaginous rings are present along the entire length of the trachea. However, they are not complete rings; they are open at the back (dorsal side).

5. **Functionality of the Open Section**: The open section at the dorsal surface allows the esophagus to expand when swallowing food. This is important as it prevents any obstruction during the swallowing process.

6. **Conclusion**: Based on the structure and function of the tracheal rings, we conclude that they are "incomplete" on the dorsal side. Therefore, the correct answer to the question is option number 3: "dorsally incomplete".