Three identical metallic uncharged spheres A, B and C each of radius a, are kept at the corners of an equilateral triangle of side d(d>>a) as shown in Fig. The fourth sphere (of radius a), which has a 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. \[\frac{qa}{2d}\left( \frac{2d-a}{2d} \right)\]
• B. \[\frac{qa}{2d}\left( \frac{2d-a}{d} \right)\]
• C. \[-\frac{qa}{2d}\left( \frac{d-a}{d} \right)\]
• D. \[-\frac{2qa}{d}\left( \frac{d-a}{2d} \right)\]