Which of the following is not a step of decomposition?

Identify the correct statements:
$A.$ Detritivores perform fragmentation.
$B.$ The humus is further degraded by some microbes during mineralization.
$C.$ Water-soluble inorganic nutrients go down into the soil and get precipitated by a process called leaching.
$D.$ The detritus food chain begins with living organisms.
$E.$ Earthworms break down detritus into smaller particles by a process called catabolism.
Choose the correct answer from the options given below:

The decomposition rate is higher when detritus is rich in:

Build up of organic material in soil occurs under which of the following conditions?

Select the incorrect option for the Detritus Food Chain $(DFC)$.

What is decomposition? Explain.