Final answer:
Methanopyrus kandleri is an archaea that produces methane, classified under methanogens within the Euryarchaeota phylum. They are known for their unique ability to reduce CO2 with hydrogen to produce methane, and they inhabit extreme environments.
Step-by-step explanation:
Methanopyrus kandleri refers to c) An archaea producing methane. This organism is part of a group known as methanogens, which are under the phylum Euryarchaeota. Methanogens are specialized archaea that reduce carbon dioxide in the presence of hydrogen to produce methane as part of their metabolic processes. They can thrive in extreme environments, such as hot springs or below freezing temperatures, and are also a component of the normal microbiota in ruminants. The ability of methanogens like Methanopyrus kandleri to capture, store, and utilize free energy offers a fascinating area of study for understanding prokaryotic evolution and the potential for life to exist in extreme environments on Earth and possibly other planets.