During a 200 m sprint, a runner's muscles receive insufficient oxygen. Which sequence best explains why the muscles eventually contract less efficiently?
Carbon dioxide accumulates, aerobic respiration stops, and body temperature falls
Oxygen accumulates, glucose is fully oxidised, and the muscle fibres cool
Ethanol accumulates, respiration releases more energy, and the muscle fibres tire
Lactic acid accumulates, the muscles become fatigued, and contraction efficiency falls
51 exam-style questions on AQA GCSE Biology 4.2 Respiration, covering 4.2.1 Aerobic and anaerobic respiration, 4.2.2 Response to exercise, and 4.2.3 Metabolism. Each one has a worked solution and a mark scheme showing where the marks go.