There has to be one side with a high concentration and another side with a lower concentration
I suggest that you should try C......
A. the kelvin temperature scale
Microevolution refers to changes that occur within a single species or group or organisms. Microevolution, as opposed to macroevolution, occurs in a short period of time. In microevolution, the ancestor and the descendant obviously belong to the same type. For example, certain pests have evolved in such a way that they become immune to pesticides; the same thing has happened to certain weeds and herbicides. Hope this helps.