A) A-Methanogenic bacteria, B-Fermentative microbes, C-$CO_{2}$ and hydrogen (biogas)
B) A-Anaerobic microorganisms, B-Methanococcus, C-$CO_{2}$ and nitrogen (biogas)
C) A-Fermentative microbes, B-Methanogenic bacteria, C-$CO_{2}$ and methane (biogas)
D) A-Aerobic microorganisms, B-Methanobacter, C-$CO_{2}$ and methane (biogas)
Explanation
The correct answer is Option C: A-Fermentative microbes, B-Methanogenic bacteria, C-$CO_{2}$ and methane (biogas).
A detailed explanation for this question is being prepared.