Brenda ran a 5 km race. during the race, she began to breathe heavily, and some of her muscles began to burn. which of these explains why brenda felt a burning in her muscles during the race? choose the correct answer. the cells did not have enough oxygen, so they used fermentation as a source of energy. the cells did not have enough glucose, so they used fermentation as a source of energy. the cells had too much glucose, so they used aerobic respiration as a source of energy. the cells had too much carbon dioxide, so they used aerobic respiration as a source of energy.