After exercising, Theo is aware that anaerobic respiration occurred in his body because his muscles ache. Which substance caused his muscles to feel sore? A-lactic acid B-glucose C-carbon dioxide D-glycogen

lactic acid

Explanation:

Lactic acid fermentation in muscle occurs during vigorous musclular activity when blood is unable to supply enough oxygen to skeletal muscles. The lactic acid might cause fatigue and result in muscle cramps. The oxygen debt incurred is paid back by the person breathing more quickly and deeply. The rate of heart beat inreases so as to transport oxygen faster to the muscle cells and lactic acid from the muscles to the liver.

During the period of paying back the oxygen debt, the lactic acid formed is oxidised to carbon dioxide, water and energy while some is taken to the liver and converted into glycogen.