Answer:
Add a 0 hour control
Step-by-step explanation:
In an experiments, a control is what serves as a guide to measure the amount of change.
An experiment is made up of independent and dependent variable
the dependent variable is the variable to be measured that is varied and in this case its the number of light while the independent variable stands alone and been depended on by dependent variable. For more precision, the varied variable should have an experimental control that will serve as a check to know if indeed the varied number of light is of significance or not. If the control is having higher average performance than the experimental variable then it shows the control is more preferably but when the performance of the variable is higher than the control then its indicates that either one or some of the variable or all are equally better than the control and can be used.