You could record how much they eat how many times they swim around in a day you could weigh your species of fish.
The answer is D
Because it is kinda basic
The nasty fine ash is the smallest of the particles produced in a volcanic eruption. It can kill you if you breathe it in:)
You can classify them in what phase they are in: solid, liquid, gas
You can classify them in Sizes
You can classify them by the number of moons they have
You can classify them by distance from the sun
You can classify them all as heliocentric or orbiting/circling around the sun
You can classify them by color
