Trachea has complete covering of cartilag rings.

Answer

### Step-by-Step Solution:

1. **Understanding the Structure of the Trachea**: The trachea, also known as the windpipe, is a crucial part of the respiratory system. It connects the larynx (voice box) to the bronchi of the lungs.

2. **Cartilage Rings**: The trachea is supported by 16 to 20 C-shaped rings made of hyaline cartilage. These rings are not complete circles; instead, they are C-shaped, which means they are open at the back.

3. **Function of Cartilage Rings**: The primary function of these cartilage rings is to provide structural support to the trachea, ensuring that it remains open and does not collapse during breathing. The C-shape allows flexibility and movement, which is essential for the trachea as it needs to accommodate the movements of the neck and changes in pressure during breathing.

4. **Height of the Rings**: Each cartilage ring is approximately 4 mm in height, which contributes to the overall strength and rigidity of the trachea.

5. **Conclusion**: Therefore, the statement that "the trachea has a complete covering of cartilage rings" is incorrect. The trachea has incomplete C-shaped cartilage rings that provide support and flexibility.