Answer:
This is an example of adaptation due to a progressive mutation
Step-by-step explanation:
At the beginning, the bacteria can use the galactose as carbon source for it needs, but since this food is getting out in every new generation. The new generations can be adapted to survive with smaller quantities of galactose until there will be one generation that can survive with any galactose source, when this offspring reach the area of the plate without galactose, then it can be grown in ant area.