Reduction of co2 to generate carbohydrates can occur when coupled to the oxidation of reduced sulfur compounds (for example, h2s). this latter process is carried out by what type of microorganism(s)

I believe that the microorganisms that carry out reduction of CO2 to generate carbohydrates coupled to the oxidation of reduced sulfur compounds are called sulfate reducers. Sulfate reducers are also called sulfate reducing prokaryotes and are composed of sulfate-reducing bacteria and sulfate reducing archaea. They can also perform anaerobic respiration utilizing sulfate as terminal electron acceptor, reducing it to hydrogen sulfide.

D)can be increased in a closed system

Less stable  hope this