Actinobacteria sp. are fermenting organisms, which do not require oxygen to survive. These organisms break down organic material and convert it to inorganic material. Which part of the carbon cycle does this describe?

Decomposition

Explanation:

The "Carbon Cycle" consists of four processes and these are: Photosynthesis, Decomposition, Respiration and Combustion.

After the process of photosynthesis, the animals will consume the plants and then will die and so will the plants after many years later. They will decompose and turn into fossil fuels, which are organic materials. The organic materials will then be decomposed by Actinobacteria into inorganic materials. These stays into the soil and allows the growth of plants once more. Then, the Respiration process follows.