The correct answer is (a) Lactic acid.
Lactic acid is a byproduct of anaerobic respiration, which is a process that cells use to produce energy when there is not enough oxygen available. When lactic acid builds up in the muscles, it can cause fatigue and muscle soreness.
Benzoic acid is a weak acid that is found in many plants and animals. It is used as a preservative and a flavoring agent.
Pyruvic acid is a chemical compound that is produced during glycolysis, the first step in cellular respiration. It is then converted into acetyl-CoA, which is used in the Krebs cycle.
Uric acid is a waste product that is produced when the body breaks down purines. It is normally excreted in the urine. However, if too much uric acid is produced or if the kidneys are not able to excrete it properly, it can build up in the blood and cause gout.
In conclusion, the accumulation of lactic acid in the muscles leads to fatigue.