A scientist studied how two enzyme-catalysed reactions progressed in separate test-tubes, X and Y. Each reaction produced colour changes that could be detected by colorimetry. $0.5\,\text{cm}^3$ samples were removed from each test-tube at the beginning of the investigation and then at regular intervals over the following 5 minutes. Copper ions were introduced into each sample immediately after collection so that the enzymes were inactivated and the reactions could not continue. The absorbance of every sample was determined with a colorimeter. The graph presents the findings from this investigation. Which statement is consistent with the results shown in the graph?
- AThe substrate in test-tube X has a higher absorbance than the product.
- BThe product in test-tube Y has a lower absorbance than the substrate.
- CThe rate of the reaction in test-tube X increased with time.
- DThe rate of the reaction in test-tube Y increased with time.