Which of the following statements provides the best analysis of what happens to freshwater lakes that are polluted by nitrates and phosphates?

Nitrates and phosphates act as nutrients, often causing algae to grow rapidly in a process called eutrophication. When the algae die, bacteria decompose them and consume dissolved oxygen, leaving less oxygen for fish and other aquatic life. So the best choice is B: nutrients promote an algae bloom, and bacterial activity reduces oxygen in the water.

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