Answer:
temperature
Step-by-step explanation:
The independent variable would be the colored water at different temperatures.
The independent variables are changeable or controllable variables supplied directly by researchers in the course of experiments. They produce effects on the dependent variable and are thus referred to as the 'cause' variable. The dependent variables are referred to as the 'effect' variables because their values vary based on that of the independent variables.
In this case, the only controlled variable of all the variables supplied by Victor is the temperature of the colored water. Changing the temperature of the colored water is expected to have effects on the time it will take for the colored water to travel to up the stalk of celery. Hence, the temperature is considered as the independent variable while the time it takes for the colored water to travel to the leave would be the dependent variable.