Question: To see patterns in the data from an experiment like this, it is helpful to graph the data. A bar graph is used instead of a line graph because each type of liver cell was independent of the others. But first, you must determine which variable should go on each axis of the graph.
What variable did the researchers intentionally vary in the experiment, and what are the units for this variable?

A. oxygen consumption rate in liver cells, in nmol O2/min • mg cells

B. concentration of liver cells, in mg/mL

C. genetic background of the rats chosen for the experiment, in type of breed

D. thyroid hormone level of the rats chosen for the experiment, in relative units