The Euryarchaeota includes all A. known thermophilic extreme acidophiles. B. the bacteria. C. known methanogens. D. green sulfur bacteria.

C. known methanogens

Explanation:

Euryarchaeota is one of the phyla included in the kingdom of Archaea. The phylum Euryarchaeota is a large phylum of archaeans and includes halophiles, all methanogens and some of the extreme thermophiles.

The archaeans that produce methane gas as a by-product of metabolism are known as methanogens. They are strictly anaerobic and can not survive in the presence of oxygen. Methanogens use hydrogen gas or acetate as an electron donor during the process of ATP formation and form methane gas.

An example includes Methanococcus jannaschii that is found near hydrothermal vents in the water heated to 85°C (185°F).