Answer: Methanogens.
- A Methanogens
- B Nostoc
- C Penicillium
- D Plasmodium
Correct answer: A. Methanogens
Explanation: Methanogens are archaebacteria found in the gut of ruminant animals (cattle, buffaloes) and marshy areas; they produce methane, a major component of biogas.
Whittaker's five-kingdom system (1969) groups all cellular life by cell structure and nutrition; viruses, viroids, and lichens fall outside this system entirely since they aren't independently classifiable as one of the five.
Concept context
Whittaker's five kingdom system covering Monera, Protista, Fungi, plus viruses, viroids, and lichens. A foundational NEET chapter on how living organisms are grouped.