The correct answer is C. A decrease in the population of sea ducks
Step-by-step explanation:
Food webs are diagrams that represent the relationship of organisms in an ecosystem by showing feeding or predatory relationships. This means food webs show which organisms eats another organism. In the case of the food web presented, this shows bald eagles fed on sea ducks and large piscivorous fish, this implies for survival bald eagles need from these two organisms. In this context, a decrease in the population of sea ducks (option C) would cause a decrease in the population of eagles because fewer sea ducks imply less food for eagles, and therefore fewer resources to survive.