During the process of photosynthesis, green plants produce... (1) sunlight
(3) nitrogen
(2) methane
(4) sugar

4

Explanation:

Plants are autotrophs, which means they produce their own food. They use the process of photosynthesis to transform water, sunlight, and carbon dioxide into oxygen, and simple sugars that the plant uses as fuel

well, that's easy; the answer's c, "it reduces contamination of the water and substrate of the estuary."