HUMAN GENERATED CO2
Option D, "increases the hydrogen ion concentration in the oceans but decreases the carbonate ion concentration and threatens the livability of the oceans for organisms that produce calcium carbonate shells," is the correct answer.
When human-generated CO2 is absorbed by the oceans, it reacts with water to form carbonic acid. This increases the hydrogen ion concentration in the oceans, which makes the oceans more acidic (lower pH). As the oceans become more acidic, the concentration of carbonate ions decreases, which can be harmful to calcifying organisms that rely on carbonate ions to produce shells and other structures made of calcium carbonate. This can threaten the livability of the oceans for these organisms.
Option A, "increases the oceanic concentration of carbonic acid," is partially correct but does not fully describe the consequences of CO2 absorption by the oceans.
Option B, "increases the oceans' acidity and pH," is also partially correct but does not fully describe the consequences.
Option C, "reduces the carbonate ion concentration in the oceans and threatens calcifying organisms in marine ecosystems," is also partially correct but does not fully describe the consequences.
