In the grids below, find how the shading of A is changed to give B. Which answer grid is related to C in the same way?

Every white cell of A is shaded in B and every shaded cell becomes white, while the grid stays in place. Doing the same to C shades exactly the four cells that are white in C: the top-middle, top-right, middle-right and bottom-left cells: (c). (a) and (d) also turn or flip the pattern, and (b) is not the reverse shading.