Answer:
Option D, fermentative bacteria.
Step-by-step explanation:
Methanogens are fermentative bacteria that oxidizes hydrogen gas and transfers electrons from H2 to CO2 to reduce itself into methane. Methanogens fall into the category of archea that work under anaerobic conditions and hence they can be termed as fermentative bacteria. Their coenzymes and electron transport processes are unique.
Hence, option D is correct.