Answer
D. It keeps chemicals from entering the watershed
Explanation
Agricultural run off can be described as the disposal of artificial fertilizers , pesticides, herbicides, sewages etc into which drained off into oceans , lakes and ponds with water .
Agricultural run off is recycled , then water will be less polluted , the water therefore be not harmful for usage by the plants/crops & it will make the drained water less contaminated for the Aquatic living in the ocean , rivers , lakes or ponds
According to Charles Darwin's theory of evolution by natural selection, organisms that possess heritable traits that enable them to better adapt to their environment compared with other members of their species will be more likely to survive, reproduce, and pass more of their genes on to the next generation. The next generation will have the things they will need to survive and the longer the generation goes the more fetchers they will have.
During normal breathing, the brain is stimulated to breath with increasing acidity as a result of CO2 concentration from basic metabolic processes. The brain is quite selfish and only really wants to maintain it's pH which should be at a range of 7.3-7.45, and will not tolerate any decrease.
In patients who have a chronic respiratory disorder with things like COPD. The brain has become accustomed to excessive acidic content, and is now stimulated by the Hypoxic drive or by low oxygen content.