Match Column-$I$ with Column-$II$. Select the option with the correct combination.

$1$. Standing state	$p$. Mass of living material at a given time
$2$. Pioneer species	$q$. Amount of nutrients in the soil at a given time
$3$. Detritivores	$r$. Species that invade a bare area
$4$. Standing crop	$s$. Breakdown detritus into smaller particles

• A
  $1-p, 2-s, 3-r, 4-q$
• B
  $1-q, 2-r, 3-p, 4-s$
• C
  $1-p, 2-r, 3-s, 4-q$
• D
  $1-q, 2-r, 3-s, 4-p$