1) rise/over = mass/volume therefore the slope represents density.
2) Formula for density:
M/V=d
A) Mass 60 g/Volume 50 mL=
Density 1.2 g/mL
B) Mass 40 g/Volume 50 mL=
Density 0.8 g/mL
C) Mass 10 g/Volume 50 mL=
Density 0.2 g/mL
Material with the highest density is Material A, and the material with the lowest density is Material C.