Concept:Match each crop correctly with the disease that commonly affects it.
Explanation:Maize is commonly attacked by smut disease, which is caused by fungi.
Sorghum is affected by smut, not scab. Scab is not a common sorghum disease.
Rice is affected by blast disease, not by black arm.
Black arm is a bacterial disease that mainly affects cotton.
Yam is affected by anthracnose, not blast disease.
Therefore, the only correctly matched pair is maize and smut.
Answer:Maize - smut