A person's heart rate while resting was measured at intervals across two 15-minute periods. In the first five minutes of the second 15-minute period, the person smoked a cigarette. The graph displays the readings obtained over the two 15-minute periods. What conclusion can be drawn from the graph?
- ACarbon monoxide affects the heart rate.
- BCarbon monoxide binds to haemoglobin increasing the flow of blood.
- CNicotine increases the heart rate so is a stimulant.
- DThe heart rate increases as a result of smoking.