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
Due to white moths being in a dark environment (from environment changes), the moth has evolved its wings to become darker. Thus blending in with its environment to be less visible to birds. A way of survival. Their adaption is the darker wings to its dark environment
B: things made of a single atom
You can use a couple of the following: Arsenic, carbon monoxide, cyanide or
mercury compounds.
