Answer:
The correct option is C) Pests have entered the bag and left waste secretions in the oatmeal.
Explanation:
Black specks are the illustration of the eggs or waste of certain kinds of pests or parasites. Black specks can also be observed in animals or humans when a certain parasite infects it. Hence, we can easily illustrate that those black specks in the oatmeal bag were due to waste secretions of a pest.
Other options, like option D, cannot be true because generally, oatmeals do not have any kind of black spots on the flakes.