The following figure depicts the outline of a large fairy ring that has appeared overnight in an open meadow,as viewed from above.The fairy ring represents the furthest advance of this mycelium through the soil.Locations A-D are all 0.5 metres below the soil surface.Responses may be used once,more than once,or not at all.

-At which location should one find the lowest concentration of fungal enzymes,assuming that the enzymes do not diffuse far from their source,and that no other fungi are present in this habitat?