# If BOD of river is high

$\begin{array}{1 1}(a)\;\text{The river is polluted with pesticides}\\(b)\;\text{Not polluted}\\(c)\;\text{Very much polluted with inorganic chemicals}\\(d)\;\text{Very much polluted with organic chemicals which are decomposed by micro-organisms}\end{array}$

Very much polluted with organic chemicals which are decomposed by micro-organisms.
Hence (d) is the correct answer.