What Would Explain the Poor Condition for Biological Productivity in the Open

Multiple Choice

What would explain the poor condition for biological productivity in the open tropical ocean?

A) Converging currents produce downwelling, thus carrying nutrients to the deep ocean.
B) Gyres contain pollution and decaying organisms that use up available nutrients.
C) Upwelling delivers seafloor sediment to the surface, thus blocking necessary sunlight for photosynthesis.
D) Strong layering isolates deep, nutrient-rich water from the sunlit ocean surface.