Urea enters the nephron through . . . . . . .
$i$. Thicker segment of ascending limb of Henle's loop.
$ii$. Thinner segment of ascending limb of Henle's loop.
$iii$. Ultrafiltration into urinary space.
$iv$. Inner medullary segment of collecting tubule.
$v$. Outer medullary segment of collecting tubule.
Select the correct option.

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