Concept:Tikka disease is a fungal leaf spot disease that mainly affects groundnut crops.Explanation:The disease is caused by the fungi Cercospora arachidicola and Cercospora personata.It produces many circular spots on the leaf surface, which later reduce the plant's ability to photosynthesise.The fungus survives in the soil or on fruit shells, and these act as sources of infection for new crops.Among the options given, groundnut is the specific crop affected by Tikka disease.Answer:C. Groundnut