That would be the helicase.
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
I'm gonna say D is the answer.
DNA polymerase is the enzyme that is responsible for adding correct nucleotide pairs to new and growing DNA strands. Mismatched base pair errors will occur if this enzymes is not able to function optimally. There are other system that work DNA polymerase, these are proof reading system and mismatch repair system. Less than optimum function of these system will lead to uncorrected mismatched base pairs.