Earthing of conductors

For zero potential of the earthed shells, why are we considering shell B as well. Shell B is grounded,sure, but it isn't connect to either shell A or C. Shouldn't we have made separate cases?
rn_image_picker_lib_temp_6fe9d9b2-4561-48c5-b12a-0505b5a184c6.jpg
Was this page helpful?