Answer :
In this experiment, the students are comparing the time it takes for each ball to fall (option B).
What is an experiment?
Experiment is a test under controlled conditions made to either demonstrate a known truth, examine the validity of a hypothesis, or determine the efficacy of something previously untried.
According to this question, a science class is conducting an investigation to see how gravity affects objects of different masses. They drop three balls from the same height and time how long it takes the balls to hit the ground.
In this experiment, the masses of the different ball is the independent variable while the time it takes for each ball to fall is the dependent variable.
Therefore, it can be said that the students are comparing the time it takes for each ball to fall.
Learn more about experiment at: https://brainly.com/question/11256472
#SPJ1