Final answer:
The right mainstem bronchus is a passage that supplies air to the right lung. The right upper lobe (RUL) is located above the carina and is closer to the trachea compared to other lobes of the lungs.
Step-by-step explanation:
The right mainstem bronchus is the passage that bifurcates from the trachea and supplies air to the right lung. It is one of the two main bronchial tubes that carry air between the trachea and lungs. The angle and distance of the right upper lobe (RUL) from the carina may vary depending on the individual. However, in general, the RUL is located above the carina, making it closer to the trachea compared to other lobes of the lungs. Therefore, the correct option would be: Option 2: How far is the RUL from carina?