Which of the following acts as $''$nature's scavengers$''$?

The process by which humus is degraded by some microbes to release inorganic nutrients is known as

$A$: Detritus food chain begins with detritus.
$R$: Detritivores like fungi and bacteria are major decomposers in such food chains.

If decomposers are removed from an ecosystem,what will happen?

Given below are two statements:
Statement $I:$
Decomposition is a process in which the detritus is degraded into simpler substances by microbes.
Statement $II:$
Decomposition is faster if the detritus is rich in lignin and chitin.
In the light of the above statements,choose the correct answer from the options given below:

Which of the following decompose the remnants of plants into $CO_2$ and water?