The correct answer is C. A decrease in the population of sea ducks
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.
A hydrometer is an instrument that measures the specific gravity (relative density) of liquids. The ratio of the density of the liquid to the density of water. A hydrometer is usually made of glass, and consists of a cylindrical stem and a bulb weighted with mercury or lead shot to make it float
I think Oxygen is the best answer.
