- A Tobacco mosaic disease
- B Potato spindle tuber disease
- C Mad cow disease
- D Rust of wheat
Correct answer: B. Potato spindle tuber disease
Explanation: Potato spindle tuber disease is caused by a viroid, discovered by T.O. Diener in 1971. Viroids lack the protein coat found in viruses.
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.