The mass per unit volume of a substance, usually expressed in grams per cubic centimeter.

• A. Core
• B. Echo Sounder
• C. Crust
• D. Density

Answer: (A)

Density is the mass per unit volume of a substance. It’s usually expressed in g/cm^3 in this context. This value shows how tightly matter is packed and is a property of the material itself, not how much you have. You find it by dividing mass by volume: density = mass/volume. For regular shapes you can calculate volume from measurements; for irregular objects, volume can be found by water displacement. In seawater, density rises with higher salinity and lower temperature, and it governs whether an object sinks or floats. So the term described is density.