Answer:
Phytoplankton feed on nutrients brought up by upwelling.
Hence, option D is the right answer.
Explanation:
Phytoplankton are microscopic marine plants, i.e they live in water bodies. They are autotrophic, i.e they prepare their own food. They are called phytoplankton because they absorb photo energy i.e sunlight. They absorb carbon dioxide and release oxygen. As they need to absorb sunlight, they are present near the surface of the water.
Upwellings are ocean currents which bring nutrients from deep cold water to the surface. Upwellings happen because of the rotation of the Earth and winds. The phytoplankton depend on the nutrients brought by the upwellings to prepare their food using sunlight and they form the food for various sea animals.