The correct option is
D All of the above
Methanogens are the primitive bacteria belonging to archaea which are able to produce methane. These organisms can utilise the carbon dioxide and hydrogen gas to form methane. These organisms are found in marshy areas where they produce the marsh gas, in swamps and in the stomach of certain animals. These organisms are responsible for methane production in the stomach of cattle which causes belching.
Thus, the correct answer is option D.