Orange rot is caused by

1. Bacteria
2. Viroids
3. Virus
4. Fungi

The correct option is D Fungi
Orange rot

Orange rot is a fungal infection caused by the fungus Alternaria citri of the class ascomycetes.

It is also known as Alternaria blotch or Black rot that occurs on citrus fruits like oranges and lemons.

As the fruit matures, it causes dark brown or black areas on the outside of it. It weakens the plant and also shortens its life span.

Final answer
(c) Fungi