Answer:
Height of marble from the ground
Step-by-step explanation:
An independent variable is the variable in an experiment that you change to see if it has an effect on the dependent variable. In this case, Jack wanted to see whether the position of the marble on the ramp (which would be the height) has an effect on the kinetic and potential energy of the marble, then the height would be the independent because it is what is being changed.
Added note:
The dependent would be the kinetic and potential energy and the constant would be the type of marble.