Answer: Chlorine
Explanation:
An independent variable can be define as changable variable, which can be used to determine it's impact over the other variable(s) in the experiment. Dependent variable cannot be changed manually instead changes occur in the independent variable is because of impact of independent variable.
In this experiment, chlorine is the independent variable. The effect of which can be observed on the hair color, which is a dependent variable.
Ice should be applied within the first 5-10 minutes after getting the injury and leave the ice for
20-30 minutes. This can be repeated every 2-3 hours or so for the next 24-48 hours.
If you consider the first 48 hours, and this timings, the frequency should be between 16 to 24 times. If you consider 24 hours, it should be between 8 and 12 times.