'Leaf curl' disease is caused by -

Correct option is C

· Correct answer: (c) Virus
· Leaf curl disease in plants, such as tomatoes and peppers, is caused by a virus, specifically the tomato leaf curl virus (TLCV) or peach leaf curl virus in certain crops.
Other options:
· (a) Fungus: Fungal infections can cause various leaf diseases but not leaf curl.
· (b) Bacteria: Bacterial infections can cause leaf spots or blights, not leaf curl.
· (d) Mycoplasma: Mycoplasma affects plants but causes different symptoms than leaf curl.