Answer: chitin.
- A chitin
- B cellulose
- C peptidoglycan
- D pure protein
Correct answer: A. chitin
Explanation: Fungal cell walls contain chitin, unlike the cellulose walls of plants.
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.