If Organic Matter Is Useful in Water as a Nutrient

If organic matter is useful in water as a nutrient source, why does excess organic matter lead to a decrease in aquatic life?

A) Aerobic bacteria feed on all the organic mater and use up all the oxygen.
B) Anaerobic bacteria feed on the organic matter and populations increase, leading to consumption of all the food.
C) Anaerobic bacteria eat all the aerobic bacteria, which leads to loss of oxygen in the water.
D) The excess organic matter blocks light, which leads to a decrease in photosynthesis and causes a drop in oxygen production.
E) none of the above