Match the ecological terms given in Column $I$ with its correct explanation in Column $II$.

Column $I$ (Terms)	Column $II$ (Explanation)
$1$. Stratification	$a$. Horizontal distribution of different species
$2$. Zonation	$b$. Rate of generation of Biomass in an ecosystem
$3$. Productivity	$c$. Breakdown of detritus
$4$. Decomposition	$d$. Vertical distribution of different species

Choose the correct option.

• A
  $1-d, 2-c, 3-a, 4-b$
• B
  $1-d, 2-a, 3-b, 4-c$
• C
  $1-c, 2-d, 3-a, 4-b$
• D
  $1-c, 2-a, 3-d, 4-b$