Correct option (b) archaebacteria
Explanation:
Methanogens belong to archaebacteria. It contains three major classes of primitive bacteria, i.e. methanogens, halophilic and thermoacidophiles.
methanogens are stuck anaerobes, present in the gut of several ruminant animals (e.g. cows, etc.) and are responsible for the production of methane gas from the dung of these animals.
Concept enhancer Halophilic bacteria usually occur in salt-rich substrate like salt marshes, etc. and are aerobic chemoheterotrophs. Thermophilic bacteria have the dual ability to tolerate high temperature as well as high acidity. These are basically chemosynthetic.
