The correct option is A a - iii, b - i, c - ii
Diseases in the plants are mainly caused by bacteria, fungi and viruses.
(a) Fungal diseases - They leave a white, black, yellow, brown spots or a fluffy or powdery coating on leaves. Ring worm is a fungal infection which produces red and itchy patches in outer skin of humans.
(b) Tikka disease - It mainly effects the roots and leaves of the plant leaving spots on them. It leads to the rottening of the roots which results in release of a foul smell.
(c) Viral Diseases -They primarily lead to the discolouration of the leaves of plants.