Concept:Stored grain pests are organisms that damage grains after harvest, like rodents and certain insects.
Explanation:Maize grain is usually kept in barns, cribs, or silos after harvest.
Rodents such as rats and mice commonly attack stored maize grain.
They feed on the grain and contaminate it with their droppings and urine.
The other options are mostly field pests.
Grasshoppers feed on leaves in the field, aphids suck plant sap, and mirids attack growing crops.
Therefore, among the given options, the rodent is the pest that attacks stored maize grain.
Answer:B. rodent