Select the correct combination of the statements (a-d) regarding the characteristics of certain organisms.
(a) Methanogens are archaebacteria, which produce methane in marshy areas.
(b) Nostoc is a filamentous blue-green alga, which fixes atmospheric nitrogen.
(c) Chemosynthetic autotrophic bacteria synthesise cellulose from glucose.
(d) Mycoplasma lacks a cell wall and can survive without oxygen.
The correct statements are?

a. Methanogens are archaebacteria belong to the domain of archaea, commonly found in wet, marshy areas, They produce methane gas.
b. Nostoc is the filamentous blue-green alga. They form gelatin body which contains trichomes.
c. Chemosynthetic autotrophic bacteria oxidized inorganic substance to produce energy. The oxidation of these substances helps in recycling of minerals. Hence they are called recyclers. But they do not synthesize cellulose from glucose.
d. Mycoplasma belongs to the smallest genus of bacteria. They do not have the cell wall and can live without oxygen.
So the correct answer is option A.