Which biotic component primarily helps in the cycling of nutrients in an ecosystem?

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

In decomposition,humus is further degraded by some microbes and the release of inorganic nutrients occurs by the process known as...

Which of the following is not true for humus?

In which layer of soil does decomposition occur at the maximum rate?

Choose the correct sentences from the options:
$(1)$ Decomposition is largely an oxygen-requiring process.
$(2)$ Warm and moist environment slows down the decomposition process.
$(3)$ Decomposition rate is slower if detritus is rich in lignin and chitin.
$(4)$ Humus is colloidal in nature and it serves as a reservoir of nutrients.