Phytoplankton are primary producers that live just below the ocean's surface. Why are phytoplankton important for the global environment?

A) Phytoplankton lower the amount of atmospheric carbon dioxide by absorbing carbon dioxide.

B) Phytoplankton increase the acidity of ocean water by absorbing carbon dioxide.

C) Phytoplankton reduce the effects of fossil fuel use by using sulfur oxides.

D) Phytoplankton provide a protein source for animals by converting nitrogen to nitrogen oxides.