Three identical metallic uncharged spheres \( A, B \) and \( C \) o...

Three identical metallic uncharged spheres \( A, B \) and \( C \) of radius \( a \) are kept on the corners of an equilateral triangle of side \( d(da) \). A fourth sphere (radius \( a \) ) which has charge \( Q \) touches \( A \) and is then removed to a position far away. \( B \) is earthed and then the earth connection is removed. \( C \) is then earthed. The charge on \( C \) is
(a) \( \frac{Q a}{2 d}\left(\frac{2 d-a}{2 d}\right) \)
(b) \( \frac{Q a}{2 d}\left(\frac{2 d-a}{d}\right) \)
(c) \( \frac{Q a}{2 d}\left(\frac{a-d}{d}\right) \)
(d) \( \frac{2 Q a}{d}\left(\frac{d-a}{2 d}\right) \)