Answer:
d. lactic acid
Step-by-step explanation:
pyruvic acid can be made from glucose through glycolysis.
Pyruvic acid supplies energy to living cells when oxygen is present (aerobic respiration), and when oxygen is absent ferments to produce lactic acid.
During vigorous exercise, there may be insufficient oxygen available to completely break down pyruvic acid for energy. As a result, the pyruvic acid is converted to lactic acid