33. apply scientific reasoning to function properly,
heart muscle cells require a steady supply of oxy-
gen. after a heart attack, small amounts of lactic
acid are present. what does this evidence suggest
about the nature of a heart attack?

As we know, lactic acid is proved as a result of anaerobic respiration. Anaerobic respiration is the type of respiration which occurs in the absence of oxygen.  Hence, the presence of the lactic acids show the supply of oxygen was not enough due to which anaerobic respiration started to take place. This evidence tells us that the nature of the heart attack is caused because of shortage or oxygen supply.