Fog begins to form when water vapor condenses into tiny liquid water droplets that are suspended in the air.
C is the answer. Due to the current state of the world economy; people, if left to their own devices, would fish as much as possible so they can sell their fish to make money. Current technology means we can catch as many fish as we want (trawlers etc.). The problem with this is that there is only a finite amount of fish in the sea. If we were to fish them without limits in place, we could cause them to go extinct.
Density is a derived unit because it's not reported as a pure unit. (A pure unit would be something like kilograms or meters.) In contrast, the units for density are kg/m3. Density is the ratio of mass to volume; mass has the unit 'kilograms' (kg) and the unit for volume is cubic meters (m3).
Density is an intensive property, which means the amount of the material is irrelevant. The density of a substance is constant.
