Answer:
The difference between the test group and the control group in this experiment would be exposure to sunlight.
Explanation:
According to the scientific method, experiments are done to prove a hypothesis right or wrong. A scientific experiment usually contains a control group and an experimental group.
To prove the above hypothesis, Carlo should have a control group which shall be given equal amounts of sunlight. Let's say 4 hours per day.
In the experimental group, the plants should be given a varied amount of sunlight, let's say one of the experimental group is given 3 hours exposure to light, the second group is given 5 hours exposure, thrid group is given 6 hours exposure.
