A student prepared two breakers with identical ounces of a water plant as shown below. She placed one beaker in the dark and the other Ik beaker beside a fluorescent lamp. She then systematically changed the distance from the beaker to the lamp. She counted the bubbles given off by the plants in each beaker. Shown here is the graph of the data for the beaker she placed beside the lamp. What was the purpose of the beaker in the dark?
A. Independent variable
B. Dependent variable
C. Control
D. Hypothesis