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.

• A
  $i, ii$ and $iii$ only
• B
  $ii, iii$ and $iv$ only
• C
  $iii, iv$ and $v$ only
• D
  $ii, iv$ and $v$ only