Final answer:
B. Sulfide
In sulfate respiration, a type of anaerobic respiration practiced by certain prokaryotes, sulfate is reduced to hydrogen sulfide to generate energy and regenerate NAD+ from NADH.
Step-by-step explanation:
In a type of anaerobic respiration known as sulfate respiration, prokaryotes, which include some species of bacteria and Archaea, derive energy by reducing inorganic sulfates. Sulfate-reducing bacteria and Archaea, most of which are obligate anaerobes, use sulfate as a final electron acceptor in their metabolic process. These organisms are capable of reducing sulfate to hydrogen sulfide as a means of regenerating NAD+ from NADH. This allows them to synthesize ATP in environments where oxygen is not present.
Therefore, the answer to the question is B. Sulfide, as prokaryotes in sulfate respiration reduce sulfate to hydrogen sulfide in their energy-producing methods.