Final answer:
The more the mass of a substance, the more volume it has, reflecting a direct relationship between mass and volume. Density is used to express this relationship as mass per unit volume.
Step-by-step explanation:
The relationship between the mass and volume of a substance is best described as directly proportional: B) The more the mass of a substance you have, the more volume you have. This means that as the mass increases, the volume generally increases as well, assuming that the density of the material remains constant. For example, doubling the mass of a substance, without changing its density, would result in doubling its volume.
The density of a substance is defined as the mass per unit volume, which is an intensive property and can be expressed as d = m/V, where d is density, m is mass, and V is volume. This relationship shows that if the mass of a substance increases while its volume stays the same, the density would increase. Conversely, if the volume increases with consistent mass, the density decreases.