From what i learned, it was thought to be CFCs (chlorofluorocarbons), so aerosol sprays i guess
The right answer is C
In the anaerobic mode, the reduction of pyruvate to lactate or ethanol (fermentations) ensures the reoxidation of NADH to NAD + consumed during the oxidation of glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate (reaction 6 of glycolysis). This regeneration of NAD + allows glycolysis to be maintained in the absence of oxygen.
In the aerobic mode, NAD + is regenerated by the respiratory chain.
Can u please make the question more clear? if u r asking which of the following is the answer ( aneurism stroke heart attach) then heart attach is the answer