To increase the validity of Mario's experiment to determine if photosynthesis is affected by the amount of light that a plant receives, the best option among the given choices is to:
Add a 0 hours control.
Here’s a detailed explanation of why this step is crucial:
1. Baseline Measurement: By including a control group where the plants receive 0 hours of light, Mario can establish a baseline measurement for oxygen production without any light exposure. This helps in understanding the inherent oxygen production levels due to factors other than light.
2. Comparative Analysis: The 0 hours control group would enable Mario to compare the oxygen produced by plants under different light conditions against a scenario where no light is provided. It acts as a reference point to more accurately evaluate the increase or decrease in oxygen production attributable to the presence of light.
3. Validity and Reliability: Adding a control group enhances the validity and reliability of the experiment. It ensures that the observed changes in oxygen production can be attributed to the variations in light exposure rather than other environmental or experimental conditions.
4. Scientific Rigor: Including a control group is a common practice in scientific experiments as it helps to eliminate potential biases and confounding variables, thereby providing more rigorous and trustworthy results.
Overall, adding a 0 hours control is essential for a comprehensive understanding of the effect of light on photosynthesis and to draw valid conclusions from the experiment.
