Geoffrey places a 9-gram piece of an unknown substance into a graduated cylinder that is filled with 12 mL of water, and the water rises from the 12 mL line to the 15 mL line. What is the density of the unknown substance? A) 108 g/mL
B) 3 g/mL
C) 0.8 g/mL
D) 0.6 mL