three identical mettalic uncharged spheres A B and C of radius a are kept at the corners of an equilateral triangle of side d (d>>a) . the fourth sphere (of radius a)which has a charge q touches A and then removed to a position far away . B is then earthed and then the earth connection is removed . c is then earthed . the charge on c is???

you said that d>>>a

then A , B, C must be like point charges itself

thereforth the charge q of the forth sphere (acting as apoint charge due to its small radius) let me call it D

The charge shall be equally distributed to both A and D and now they will be possessing charge q/2

since d>>>a there can be no electromagnetic induction and hence i say without any proof of my result that C and B are remained uncharged iff (if and only if) d>>>a...

I take no certainity ofthe above solution if d and a are of the same order of magnitude.(Scientifically)