In the following groups of materials, which group contains only non biodegradable items.

Question

$\begin{array}{1 1} (a)\; \text{Polythene, Detergent, Leaf} \\ (b)\; \text{Wood, Paper, Leather} \\ (c)\; \text{Plastic, Detergent, Grass} \\ (d)\; \text{Plastic, Bakelite, DDT} \end{array}$