Final answer:
Object B has a greater density than object A by 1 g/cm³, calculated by dividing the mass of each object by their volume which is the same for both objects.
Step-by-step explanation:
The question asks us to compare the density of two objects based on their mass and volume. Density is defined as the mass of an object divided by its volume. To find the density of object A, we divide its mass (12g) by its volume (8cm³) which gives us a density of 1.5 g/cm³. For object B, we divide its mass (20g) by the same volume (8cm³), resulting in a density of 2.5 g/cm³. Therefore, object B has a greater density than object A, and the difference in density is 2.5 g/cm³ - 1.5 g/cm³ = 1 g/cm³.
The correct answer is C. Object B, by 1 gram per cubic centimeter.