Question: Base-richness in ecology is the level in water or soil of chemical bases, such as calcium or magnesium ions, changes in the levels of acids (such as dissolved carbon dioxide) may significantly change acidity without affecting base-richness, Carbonic acid is a chemical compound with which chemical formula ?
{'answer': 'HCO', 'supporting_facts': [['Base-richness', 4], ['Carbonic acid', 0]]}