Answer: Option C
Explanation: The carbon dioxide is major green house gas that traps heat. But due to global warming the amount of carbon dioxide in the environment is increasing day by day.
The carbon dioxide gets in the ocean water and harms the organisms present in the ocean water. The coral present inside the water covers a very large area and is a major part of the marine ecosystem.
The carbon dioxide in excess leads to coral bleaching. This is a phenomenon in which the algae that is found inside the coral leaves the coral due to stress condition.
Thus, carbon dioxide in water increase the acidification in ocean which leads to coral bleaching.