Question

which material should not be present in garbage for its proper microbial decomposition

Answer 1

We know that proper microbial decomposition is possible only for waste which can be decomposed, like organ waste by bacteria, or by any other means.

Since,$\textbf{ non-biodegradable}$ waste material should not need to be present in garbage for proper microbial decomposition.

Answer 2

biodegradable waste material should not be present in garbage for proper microbial decomposition.