What is the number of lobes in the right and the left lungs respectively?

Alveoli are tiny, balloon-shaped air sacs that sit at the very end of the respiratory tree, branching off the _______.

The opening between the vocal folds is called:

An important region of the body located between the lungs, where structures like the heart lie, is known as:

Lungs do not collapse between breaths and some air always remains in the lungs which can never be expelled because
1. there is a negative pressure in the lungs
2. there is a negative intrapleural pressure pulling at the lung walls
3. there is a positive intrapleural pressure
4. pressure in the lungs is higher than the atmospheric pressure