What is the number of tracheal cartilaginous rings in humans?

Select the correct option for the trachea.

The lungs are composed of $........$.

The given figure shows the human respiratory system with structures labeled $A, B, C,$ and $D$. Which of the following options correctly identifies the structure and its main function or characteristic?

Which of the following structures is present inside the larynx of the respiratory system?

The narrowest and most numerous tubes of the lungs are termed as: