Biology

Lactic acid fermentation occurs in muscles during intense exercise when oxygen is in limited supply. During high-intensity activity, the muscles require more energy than can be provided through aerobic respiration alone. Since oxygen is not available fast enough to meet the demand, the muscle cells switch to lactic acid fermentation to continue producing ATP, resulting in the production of lactic acid as a byproduct.

The other options are incorrect:

Option A: The problem during intense exercise is not the lack of glucose.