Final answer:
The SI Unit for density is Kilogram per meter cubed (kg/m^3). For practical use, g/cm^3 and g/L are also commonly used for solids, liquids, and gases respectively.
Step-by-step explanation:
The SI Unit for density is a) Kilogram per meter cubed (kg/m^3), which is the correct answer to the student's question. Density is defined as the mass of a substance divided by its volume, and the SI units for mass and length are kilograms (kg) and meters (m), respectively. Therefore, the density is expressed in kg/m^3. Although this unit is standard, in practical laboratory contexts, density is often reported in grams per cubic centimeter (g/cm^3) for solids and liquids, or in grams per liter (g/L) for gases. For instance, the density of water at room temperature is about 1 g/cm^3, which is equivalent to 1000 kg/m^3. This conversion factor can be useful when needing to relate common laboratory measurements to the standard SI unit.