A lifeguard practises towing a training manikin across a pool for 90 seconds. Before the drill, the lifeguard's oxygen uptake is 0.28 dm³ per minute.
Oxygen uptake is measured during four one-minute intervals after the drill.
| Time after drill in minutes | Oxygen uptake in dm³ per minute |
|---|---|
| 0–1 | 1.20 |
| 1–2 | 0.74 |
| 2–3 | 0.41 |
| 3–4 | 0.28 |
Which inference is best supported?
The oxygen debt was probably greatest in the final interval because oxygen uptake was lowest
The oxygen debt was probably repaid by the final interval because oxygen uptake had returned to its pre-drill rate
The muscles probably stored extra oxygen during the second interval for use in the final interval
The muscles probably produced carbon dioxide by anaerobic respiration during the first interval
92 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.