Answer:
Mass
Step-by-step explanation:
Usually, you plot the independent variable along the horizontal (x) axis and the dependent variable along the vertical (y) axis.
Marcia's teacher plotted the mass of the sample along the x-axis and volume along the y-axis.
The mass is the independent variable, because that is what the teacher varied.
The volume is the dependent variable, because it depends on the mass.
Sample number is wrong, because it is not a variable.
Substance is wrong, because all samples consist of the same substance.
Density is wrong, because it is constant. It is the slope of the graph.
