Answer: obligate parasites.
- A obligate parasites
- B free autotrophs
- C free-living cells
- D soil decomposers
Correct answer: A. obligate parasites
Explanation: Viruses are obligate intracellular parasites, inert outside a host.
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.