ANSWER:
Burning of fossil fuels has contributed most to the 'acidification of lakes' in Adirondack region.
EXPLANATION:
When 'fossil fuels are burnt', they release air pollutants that contain nitrogen and sulphur. These elements form nitrogen dioxide and sulphur dioxide when they are released into the air. Further, these gases react with water to form acids. This acid then falls along with precipitation when it rains and that is why rain is called acid rain. This acid rain results in the deposition of acids on the surface of water bodies as well as other landforms on the earth.