Which portion of the human respiratory system is called the sound box?

The total surface area of the human lungs,specifically the respiratory surface area provided by the alveoli,is approximately: (in $; m^{2}$)

Number of alveoli in human lung is about

What are the membranes covering the lungs called?

Friction on the lung surface is reduced by:

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.