Where is mucus found in the human body?

Select the correct statements about alveoli from the following.
$i$. Air sac of each terminal bronchiole shows $10$ to $12$ alveoli.
$ii$. Each alveolus is surrounded by a network of capillaries.
$iii$. They are lined by ciliated pseudostratified epithelium.
$iv$. They provide surface area for exchange of gases.
$v$. There are about $700$ million alveoli in the lungs.

The larynx is a modified part of which structure?

Number of alveoli in the human lungs has been estimated to be approximately

Pulmonary artery drains the deoxygenated blood from

The function of surfactant is/are: