Biology

The correct answer is:

A.This run-off makes it to a body of water, where toxic algae blooms feed on excessive amounts of added nutrients.

Fertilizer-based nutrients like phosphates and nitrates are commonly found in agricultural run-off, and when these nutrients enter rivers, lakes, or coastal waters, they can cause eutrophication—a process in which the excessive nutrient load promotes the rapid growth of algae. This is often referred to as algal blooms. When these blooms die and decompose, they consume large amounts of oxygen in the water, creating "dead zones" where aquatic life (such as fish and invertebrates) cannot survive due to the lack of oxygen. Some algal blooms can also produce toxic compounds, which further harm aquatic ecosystems and can pose risks to human health.

Breakdown of the other options:

B.These nutrients are toxic to plants and algae: While excess nutrients can lead to harmful algal blooms, nitrates and phosphates themselves are not inherently toxic to plants or algae in moderate amounts. It's the excess of these nutrients that causes problems, not the presence of nutrie...